Mathematics for IGCSE & O level - Coordinate Geometry (Section 4 - No. 32)
What is the relationship between the gradients of two perpendicular lines?
They are equal.
They multiply to -1.
They add to 0.
They are reciprocals.
คำอธิบาย
Perpendicular lines have gradients that are negative reciprocals, and their product is -1.