perplexus.info :: Just Math : It's obvious, but needs proof

It's obvious, but needs proof (Posted on 2017-03-15)

Let points A, B, and C be equally spaced around a circle, and let point P lie on the arc between A and B.

Prove that PA + PB = PC.

See The Solution Submitted by Ady TZIDON

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Solution

| Comment 1 of 4

Ptolemy's theorem gives

PC*AB = PA*BC + PB*CA

Points A, B, and C equally spaced

around the circle gives

AB = BC = CA

Therefore,

PC = PA + PB

QED

Posted by Bractals on 2017-03-17 15:17:05

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