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What is the length of the tangent segment from a circle to a common external point.

What is the length of the segment of two tangent lines to a circle of known radius which meet at a known known angle at a common external point?

In the following link, what is the length PN (or PM) given the angle NPM and radius of the circle?

equal tangents


$$PM=R\cot\frac{\angle NMP}{2}$$