Slope of Perpendicular Lines

📌 CONCEPT: The slope of two perpendicular lines is the negative reciprocal of each other, which means if one line has a slope 'm', the other line will have a slope of -1/m.

📐 RULE / FORMULA: The product of the slopes of two perpendicular lines is -1, i.e., m1 * m2 = -1.

💡 WORKED EXAMPLE: Let's say the slope of the first line is 2 and the slope of another given line is -1/2. To show that the slope of the line perpendicular to the given line is 2, we use the formula m1 * m2 = -1. If m2 = -1/2, then 2 * m1 = -1. Solving for m1, we get m1 = -1/2, which is the negative reciprocal of 2.

⚠️ COMMON MISTAKE: Students often confuse the concept of negative reciprocal with the concept of negative slope. Remember, negative reciprocal means the product of the slopes is -1, not just one of the slopes is negative.