Need to know how to determine the equations of trigonmetric functions by inspecting their graphs? Learn how. 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 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 calculate the equations of trig functions by looking at their graphs.