3 Given Points

Question

Given three points D(2, 5) E(-2, -3) and F(4, -6) determine whether or not the line through D and E is perpendicular to the line through E and F?

Answer 1

For two lines (neither of which is vertical) to be perpendicular, the slopes of the lines must be negative reciprocals.  

 

Slope of line through D and E is (-3-5)/(-2-2) = 2

 

Slope of line through E and F is (-6-(-3))/(4-(-2)) = -1/2

 

Since the slopes are negative reciprocals, the lines are perpendicular.