Mathematics for IGCSE & O level - Coordinate Geometry (Section 2 - No. 25)
What is the relationship between the gradients of two perpendicular lines?
They are equal.
Their product is 1.
They are reciprocals.
Their product is -1.
Erläuterung
The gradients of perpendicular lines are negative reciprocals of each other, and their product is -1.