In this video the instructor shows how to find out an equation of a perpendicular line. If you need to find the equation of a line passing through the given point and is perpendicular to another line, the first thing you need to do is compute the slope of the given line. Obtain the slope of the equation by writing it in the form of y = mx + b. Now the product of slopes of two perpendicular lines is a negative one. So the slope of our required line will be the negative inverse of the slope of given line. Now you have the point and slope of the required line. Substitute these values in the slope-point general equation giving you the equation of the perpendicular line. This video shows how to compute the equation of a perpendicular line.