Constructing Perpendicular Lines in the Coordinate Plane (Slope & Orthogonality)

This example demonstrates how to define and construct a perpendicular line on the coordinate plane using slope and orthogonality, then validate the result by measuring the included angle. It centers on key ideas from coordinate geometry: the definition/properties of parallel and perpendicular lines, slope (m) relationships, the orthogonal-line construction, and using angle measurement to confirm that two lines meet at a right angle. Construction in GeoGebra is built from: Line for creating lines, Point for specifying points that determine line positions, Slope to obtain/represent slope information, OrthogonalLine to generate the line through a chosen point that is perpendicular to a given line, Angle to measure the angle between the two lines, and FractionText to display exact slope values or key fractions. Labeled objects (e.g., points like A, B, C, D and multiple text labels) support interactive questions and quick discovery. Suitable for middle and high school students, classroom demonstrations, and self-guided practice on slope, perpendicularity, and geometric construction.