Prove that the straight-line drawn perpendicular to a radius of a circle at its extremity is a tangent to the circle. Use Algebra only

Question

Prove that the straight-line drawn perpendicular to a radius of a circle at its extremity is a tangent to the circle.  Use Algebra only

crashonce · Answer

@Directrix

directrix · Answer

We're having an epidemic of coordinate Geometry proofs. :)

@CrashOnce   I left a question for you about the Angle Bisector Theorem proof in another thread.

mathmate · Answer

"A tangent to a circle is perpendicular to the radius at the point of tangency. "
Isn't the line is a tangent by definition?

anonymous · Answer

basically it just asks you to prove that a tangent is 90 degrees to a radius

solomonzelman · Answer

|dw:1420078749119:dw|to prove it? don't really know....

crashonce · Answer

@TuringTest

jhannybean · Answer

|dw:1420079566861:dw| Maybe,