30.4 The Circle: Equation and Positional Relationships
Point 6 of 6
30.4.6 Tangent Lines and Chord Length
Core idea
From a point outside the circle two tangent lines reach out like arms; a chord is bisected by the perpendicular, so use d and r to build a right triangle and find its length.
Module goal. Write the set of points equidistant from a fixed point as an equation, master the circle's two forms, and judge tangency and intersection with lines and other circles.
eastmath.com · 30.4 The Circle: Equation and Positional Relationships · 30.4.6 Tangent Lines and Chord Length