Traditional Culture Encyclopedia - Photography and portraiture - Tangent line of photography theorem

Tangent line of photography theorem

Method 1: Find the distance from point C to straight line AB in right triangle PAC by projective theorem, and then use Pythagorean theorem.

Method 2: Subtract the two circular equations through the circular equations of P, A, C and B to get the straight AB equation, and then use the Pythagorean theorem by using the distance from the point to the straight line.