For Masters Only. Math Olympiad Question

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This is math olympiad question. Nice algebra problem. How to solve it? You should learn this trick.
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Draw a 72 - 72 - 36 triangle. This is a golden ratio triangle. Draw a segment bisecting the 36 deg angle. You have 2 right triangles. The sin(18) = 1/2 / (1 + sqrt(5))/2. Simplify to get (sqrt(5) - 1)/4.

raymondarata
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And for sin 23°, how to procide to find that?!

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