Now that we've learned what perpendicular lines have in common, let's see if we can use that knowledge to create the perpendicular to a given line.[br][br]Spend a few moments adjusting the blue line on the graph in the interactive below, and see if you can make it perpendicular to the red line. The slider bar marked slope will let you manipulate the slope. First, figure out the slope of the red line, then change the value of the slope to the opposite reciprocal of that number. Do the lines look perpendicular to you now? When the lines are perpendicular the text that says "Not Perpendicular" will switch to "Perpendicular!".[br][br]Now try changing the value of the y-intercept of the blue line. Do you see that there are an infinite number of perpendicular lines? It doesn't matter what the y-intercepts are, lines are perpendicular as long their slopes are opposite reciprocals of one another.[br][br]When you have successfully created a perpendicular line, click the New Line button to try again with a different line. Try to successfully create 3-5 perpendicular lines before you move on.

This applet created for use in Algebra 1 at Michigan Virtual School. [url]http://www.mivhs.org/[/url]