Parallel and Perpendicular Lines (Leaving Cert Mathematics): Flashcards

Equal slopes ($m_1 = m_2$)

Right angles (90°)

$m_1 \times m_2 = -1$

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

$-\frac{a}{b}$

Find slope of given line, use same slope

Find slope, then calculate negative reciprocal

$y - y_1 = m(x - x_1)$

$-\frac{b}{a}$

Multiply slopes; product should equal $-1$

Never meet

Negative reciprocals of each other