10.3 Slopes of Perpendicular Lines

This GeoGebra example demonstrates the relationship between the slopes of two perpendicular lines, showing that their slopes are negative reciprocals of each other. The core mathematical concept is coordinate geometry, specifically the condition for perpendicularity: if two non-vertical lines have slopes m1 and m2, then m1 * m2 = -1. The construction uses the Polygon command to create a polygon, the Angle command to mark relevant angles, and multiple points (A, B, C, D) along with line objects (a, b, c, d, etc.). Text objects (text1 through text7) display the slope values and the relationship. This resource is suitable for high school or early college students learning analytic geometry, and can be used by teachers for classroom demonstrations or by students for independent exploration of perpendicular line properties.