# Hot Math Posts

### How To: Calculate the circumference of a circle

This video shows how to calculate the circumference of a given circle. The video first describes the circumference or perimeter of a circle as the distance around the outside of a circle. To find the circumference we need either the radius or the diameter of the circle. When you know the diameter of the circle, the formula to find the circumference denoted by 'C' is 'pi' times the diameter, where 'd' is the diameter and 'pi' is a constant, the approximate value being 3.14. And when you are gi...

### How To: Evaluate logarithms using a calculator TI-83

A video to help calculator users find the natural logarithm (log base e, or "ln") and standard logarithm (log base 10, or simply "log") of any number using a TI-83 calculator (works for any issue of the TI-83 calculator or even a TI-84 calculator). Turn on your calculator. To find the natural log of a number, press the "ln" button (the third button from the bottom left), enter the number you want to find the natural log of, press the ")" (closed parenthesis) button, then press enter. The same...

### How To: Translate a sentence into math symbols

We will be translating the sentence "twice y differs from 5 by more than two, “into a mathematical equation. The word twice generally means two times, so 2*y (because y comes next in the sentence). Differs normally means is different and a difference from something in a mathematical sentence means subtraction most of the time, thus minus five. We don't know if we’re talking about below 5 or above 5 on the number line, so we put absolute value around the equation. More than implies a greater t...

### How To: Estimate probabilities with the empirical rule

Learn how to use the empirical rule (or 68-95-99.7 rule) to estimate probabilities for normal distributions in statistics. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of fre...

### How To: Graph square root functions & inequalities

On Yay Math, Robert Ahdoot, founder of Yay Math, will show you some square root functions and some inequalities. He begins with the problem y=x². Then he makes a sketch with two intersecting lines in a t shape. The problem is illustrated by a curved U shape, the U's bottom resting on the horizontal bar, which represents x, while the center takes the vertical line. The vertical bar represents y. This U is directed up because the x² is a positive number. If the number were negative, the U would...

### How To: Use cross products to solve proportions

To solve a proportion for a variable you should employ cross multiplication. The basis of cross multiplication is the property which states that the product of the numerator of one fraction and the denominator of what it is set equal to is equal to the product of the remaining denominator and numerator. For example if you have x/15=21/45 you simply need to multiply x by 45 and 15 by 21 then set them equal to each other. The result of this is 45x=315. To solve this new problem for x, divide bo...

### How To: Find the slope's unit of measure

This educational video from free math tutoring shows how to calculate the slope of a line and assign units to the answer obtained. This video assumes that the viewer is familiar with the concepts of axes and co-ordinate geometry. The narrator uses a commonly used formula to calculate the slope of the line in the first section of the video. In the second section, the narrator demonstrates how to assign units to the answer, as per the question asked.

### How To: Solve inductive reasoning problems in math

From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to solve and work with problems involving inductive reasoning in math.

### How To: Evaluate combinations of functions from graphs

YouTube user NotesCollegeAlgebra teaches you how to evaluate combinations of functions from graphs. You start off with a graph and some functions. (f+g)(-3), (g/f)(0) and (fg)(-6). You start looking at the graph and the first line and you get (f+g)(-3)=f(-3)+g(-3)=3+1=4. (g/f)(0)=g(0)/f(0)=2/-3=-2/3. (fg)(-6)=f(-6)g(-6)=(-3). But then when you want to find out g(-6) you realize -6 is not in g's domain. So the answer to the last equation is that it doesn't exist.

### How To: Simplify square roots in less than a minute

A square root of a number is a value which when multiplied to it self gives you the original number. The square roots of perfect squares are whole numbers. Like square root of 9 is 3, because 3 times 3 is 9. Similarly square root of 81 is 9 because 9 times 9 is 81. Others numbers do not have a perfect square root and in those cases you can only simplify the number to an extent. So to find out the square root of any number first you need to factorize that number. Factorize the number into smal...

### How To: Figure out a tip without a calculator

To figure out a tip without a calculator, first remove the pennies amount in the bill. For example, if your bill is $23.76 becomes $23.70. To figure out a 10% tip, move the decimal point one place to the left. So, 23.70 becomes 2.370 or $2.37. Bump up that number to $2.30 or $2.40 or $2.50 cents, depending on your preference. Since 20% equals two times 10%, double the figure you computed for 10%. So, $2.30 becomes $4.60, or $2.40 becomes $4.80 or $2.50 becomes $5.00. Using this method, you wo...

### How To: Solve complex indefinite integrals in calculus

In this video the math teacher explains the meaning of the indefinite integral formula in calculus by stating it in terms of antiderivatives. He then shows in general terms how this indefinite integral formula has a related derivative formula, i.e. if the derivative of F(x) is f(x) then the indefinite integral of f(x) is F(x) plus a constant term (C). With this general relationship the teacher takes us through three related examples where he converts a derivative formula to an integral formul...

### How To: Find the vertical asymptotes of a rational function

Need help figuring out how to find the vertical and horizontal asymptotes of a rational function? Learn how with this free video lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Calculate azimuth in trigonometry

Azimuth is simply the angle of an object in the sky along the horizon. Yes, it's spherical trigonometry but it's not difficult! Check out this video and in just a few minutes you will be able to solve azimuth problems on your own.

### How To: Work with complex numbers

In this algebra video the instructor shows how to work with complex numbers. When you have a positive number under the square root, you can easily find its value by writing it in the form of product of numbers, and then solving. That is, to find the square root of a positive number, you can find another number which multiplied by itself gives the original number. This new number becomes the square root of the original number. But when you are asked to find out the square root of a negative nu...

### How To: Evaluate a telescoping series using partial fractions

Looking for a primer on how to solve a telescoping series using partial fractions? See how it's done with this free video college algebra lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Graph trigonometric functions

Learn how to graph the amplitude and periods of sine and cosine functions in basic trigonometry. Learn how to use trigonometric functions to calculate the sides of a right triangle. Need to know how to solve a matrix-form linear equation in algebra? From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your h...

### How To: Find percent

Finding the percent of a given value is made simple and easy in this math tutorial video. In step one you must divide the part or the portion by the whole. As a result we obtain a decimal number. In step two, we must then move the decimal point two places to the right in order to convert the number into a percent value. This brief video tutorial illustrates the process in these two steps and makes it simple for anyone to be able to obtain a percent value for a portion of a whole.

### How To: Find points on y-axis a certain distance from a point

This is video on mathematics. It specifically deals with geometry. The video describes how to determine where the y-intersects are when a point and distance to the y-intersect are given. The author starts out by giving an example ordered pair. The speaker next shows an example of how to solve such a problem. The speaker uses the distance formula along with the given distance and x-coordinate in order to solve for the y-intersect values in question. Most of the video entails solving this example.

### How To: Analyze trigonometric functions graphically

Watch to learn how to use graphs to help analyze sine, cosine, and tangent functions in trigonometry.

### How To: Find the surface area of a cone without slant height

Math always seems hardest until someone shows you how to do the problem and then it all seems just so simple. This video will walk you through the process of finding the surface area of a cone when you also have to derive the slant height. Use this example to help with your other cone problems.

### How To: Calculate percent error in chemistry lab activities

If you want to know how to calculate percent error easily, you should watch this video. Error is the amount of deviation from accurate values. Error calculation is not possible, unless you make a quantitative measurement of the various quantities involved in your experiment. Measurement can help us in calculating errors and knowing how right we are in our theoretical models. In calculating percent error, We need to get the experimental value and the value which you are aiming at, which is the...

### How To: Do long division with remainders

This video goes through the step by step process of doing long division with remainders. Multiple examples are used throughout the video to give the viewer a better idea of how to properly complete the difficult task. Perfect for anyone learning long division for the first time, or for anyone attempting to relearn long division after forgetting how to do the process (an all to common occurrence in a world with calculators on every cell phone).

### How To: Use a unit circle to find trig values

In this tutorial, we learn how to use a unit circle to find trig values. The unit circle has a radius one, use the definition of the trig functions to figure this out. Write them down if you need to, to remember what they are. You will also need two special triangles to help figure this out. Make sure you know the short side is opposite 30 degrees. Now, draw out your graph and find the ordered pair of pie, then find the y value of it. From here, find the cosine, tangent, and other units using...

### How To: Find a missing vertical angle

This video shows how to solve a very basic yet very important geometric problem which is, finding a missing angle of a triangle. This videos shows the viewers more than one basic information about the triangle. It is a short and simple example which is very much helpful for the students who are beginners in geometries and it can be a very useful tip for the people going for interviews since they need to know these basics to solve some very critical puzzles.

### How To: Solve a system of linear equations with a TI-89

Looking for instructions on how to solve systems of linear equations using a TI-89 graphing calculator? Learn how with this free video algebra lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Draw a perpendicular line from a point on a line

For people who are learning how to do basic geometry, this video will show you how to draw a perpendicular line from a point on a line using only a compass and pencil. You should first take your compass and place it on the center of the point on the line, drawing an even semicircle around the point. Then, finding the points where the semicircle intersects your original line, place the center of your compass on this point and then draw some arcs over where your point is. Repeat this on both si...

### How To: Calculate the area of irregular shapes

In this tutorial the instructor shows how to compute the area of irregular shapes. He demonstrates this with an example showing an irregular area and says that as there is no direct formula to calculate it, you need to break up the irregular area into identifiable simple geometric figures. He goes on and breaks the irregular shape into a square, a triangle and a trapezoid. Now he computes the individual areas using a standard formula and sums them up to arrive at the final complete area of th...

### How To: Calculate the volume of a triangular solid or triangular prism

With mathematics, as with anything else, not everyone progresses at the same rate. Geometry is no exception. Happily, in the age of Internet video tutorials, this isn't a problem. Those who progress quickly can go beyond what's being taught them and those who are struggling likewise have all the time in the world to catch up. With this free video math lesson, you'll learn how to calculate the volume of a triangular prism.

### How To: Solve rational equations easily

This video revolves around solving rational equations in Algebra 2. When you are given a rational equation, you have to find the greatest common factor and multiply all fractions to get that common factor. If a fraction already has that common factor, then no further step is necessary for that one. Next, you have to multiply all fractions by the greatest common factor to get rid of all denominators. Finally, the remaining equation is simple math and you only need to solve the equation for the...

### How To: Solve percent proportions

A percent problem is one in which you are given a quantity and asked to compute the value of a percent of it. You may also be given the whole quantity and a part of it and asked to compute the percentage of the part in the whole. To do these kind of problems you need to use the rule which states that the ratio of the part to the base it equal to the ratio of the percent to hundred. That is part/base = percent/100. This comes from the definition of percentage which states that percentage is eq...

### How To: Understand and find x and y intercepts

In this tutorial the author explains about the concept of X and Y intercepts in coordinate geometry. She uses a graph consisting of a line to explain the concept. She tells that Y intercept of a line is nothing but the value of Y coordinate where the line crosses the Y axis. Similarly she tells that X intercept is the x coordinate of the point where the line crosses the x axis. She demonstrates this example using a graph tool. In this video the tutor shows how to find the X intercept and Y in...

### How To: Perform mental subtraction for math class

Having problems with subtraction. For some people, mathematics doesn't come easy, but there are tricks to solving certain problems, like subtraction. Check out this math video tutorial to learn how to perform mental subtraction for math class.

### How To: Divide small numbers by big numbers

This is a mathematical educational video on how to divide a small number by a larger number. You are aware that it is easy to divide a larger number by a small number. For example, if you want to divide 379 by 9 it is easy to do so. But if you have to divide 9 by 379 it is a bit difficult. You have to add a zero and see if you can divide. You need to add one more zero so that you can divide 900 by 379. But you should know that the answer would start like this 0.0 as we have added 2 zeros alre...

### How To: Find the area of a triangle when given 2 sides & angle

This video shows you how to easily find the area of a triangle when you know the length of 2 sides and the angle between them. The first thing you have to do is mark the sides of the triangle by a, b, c, where a is the side between A and B, b is the side between B and C and c is the side between C and A. If you know 2 of these 3 sides an you know the angle between them you can find the area of the triangle very simple: Area= (a x b x sin c)/2, where a, b are the two sides and c is the angle b...

### How To: Find the area of a parallelogram using geometry

The video shows us how to find the area of parallelogram using geometry. Here in this video it is done by using an example where the parallelogram is given ABCD. The area of the parallelogram is base times height (bh). Here the base is given as 15 but the height is not known but it is represented by the segment BD. To find the value of h, let’s use right triangle BDC on the right side of the figure. Since base is 15 and the opposite side of the parallelogram is congruent, the hypotenuse of th...

### How To: Find the area of an oblique triangle using formulas

In this tutorial the instructor shows how to find the area of an oblique triangle using different formulas. To find the area of an oblique triangle there are different formulae. The first formula to calculate the area of a triangle is area A = (1/2) * a * b * Sin(C), where a and b are the lengths of the two sides of the triangle and C is the value of the angle of the triangle that lies in between the two sides a, b. Now substitute these values in the given formula to find the area if you have...

### How To: Calculate the height and volume of a pyramid

Need to know how to calculate the height and volume of a pyramid in geometry? Learn how with this free video lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Solve equations with the order of operations

In mathematics, the order of operations define the priority in which complex equations are solved. The top priority is your parenthesis, then exponents, followed by multiplication and division, and finally addition and subtraction (PEMDAS). This video tutorial demonstrates the order of operation with various examples and explains the associated methodology. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autod...

### How To: Find the Slope Given 2 Ordered Pairs

Slope is the change in Y over the change in X. Written out, the formula looks is as follows: (y2-y1)