If you want to draw a perpendicular line from a point on a line, you would measure a 90 degree angle from that point and then draw the line outward.
Explanation
On the other hand, if you wanted to draw a perpendicular line connecting a line and a point off of the line, you would have to connect the point to the location on the line that forms a 90 degree angle.
Both methods involve making a 90 degree angle between two lines. Can you think of any other similarities?
