Perpendicular Lines (Grade 11 NSC Matric Mathematics): Flashcards

90 degrees (right angle)

$m_1 \times m_2 = -1$

$m_1 = -\frac{1}{m_2}$

Flip the fraction and change the sign

Write given line in standard form $y = mx + c$

Use $m_1 = -\frac{1}{m_2}$ to find perpendicular gradient

Use gradient-point form $y - y_1 = m_1(x - x_1)$

Vertical or horizontal lines

$m = \tan \theta$

Negative reciprocals of each other