Two lines are perpendicular if the product of their slopes is -1. That is, if one line has slope m₁ and the other has slope m₂, then m₁ × m₂ = -1. Alternatively, if m₁ = a/b, then m₂ = -b/a (negative reciprocal). For vertical and horizontal lines: a vertical line (undefined slope) is perpendicular to a horizontal line (slope 0).

Break down complex topics into smaller, manageable chunks for easier recall.

Zambia

• ivwananji siwale – 29 pts

• Mid-point of A Line
• Equation of a Straight Line
• Parallel and Perpendicular Lines
• Area of Rectilinear Figures
• Distance of A Straight Line