An angle is formed by two rays (arms) from a vertex V. Its bisector — the ray splitting the angle into two equal halves — is drawn. Drag the point P inside the angle, or drag the arms. The perpendicular distance from P to each arm is shown. P is the same distance from both arms exactly when it sits on the bisector. A toggle snaps P onto the bisector so the two distances always match. An info button opens a drawer explaining the idea.