Mathematics

Two perpendicular lines have a special relationship between their slopes that comes from the geometry of right angles. If you rotate one line 90° to get a perpendicular line, the slope transforms in a very specific way: the new slope becomes the negative reciprocal of the original. This means if one line has slope $m_1$, the perpendicular line must have slope $m_2 = -\frac{1}{m_1}$, or equivalently, $m_1 \cdot m_2 = -1$.

Two perpendicular lines have a special relationship between their slopes that comes from the geometry of right angles. If you rotate one line 90° to get a perpendicular line, the slope transforms in a very specific way: the new slope becomes the negative reciprocal of the original. This means if one line has slope $m_1$, the perpendicular line must have slope $m_2 = -\frac{1}{m_1}$, or equivalently, $m_1 \cdot m_2 = -1$.