2. A (4, 4) D (-4, 4) B (4, -4) C (-4, -4) 90 0 90 0
3. Perpendicular Lines 0 y x A (a , b) B (-b , a) After a 90 0 rotation (anti-clockwise) A moves to B As both lines go through origin gradients are: 90 0 NB Fraction has been turned upside down and turned into negative
4. Copy the following: For perpendicular lines: 1. Lines are perpendicular 2. To find gradient of line perpendicular to given line think: “ Flip the fraction and change the sign”
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7. Example 2 Two lines have equations 3x + 2y - 7 = 0 & 4x - 6y + 1 = 0 Prove that they are perpendicular. Solution : 3. Check that m 1 x m 2 = -1 4. Make statement Since m 1 x m 2 = -1 lines are perpendicular