Mathematics for IGCSE & O level - Coordinate Geometry (Section 1 - No. 38)
Which of the following is true for two perpendicular lines?
They intersect at a right angle.
Their slopes are equal.
The product of their slopes is -1.
Their y-intercepts are always different.
ব্যাখ্যা
Perpendicular lines have a product of slopes = -1