# Sum of sines.

• Feb 26th 2011, 10:18 AM
arm
Sum of sines.
Prove: $sin (\frac{\pi }{25}) + sin (\frac{2\pi }{25}) +...+ sin (24\frac{\pi }{25})=cotg\frac{\pi }{25}$
• Feb 26th 2011, 12:59 PM
mr fantastic
Quote:

Originally Posted by arm
Prove: $sin (\frac{\pi }{25}) + sin (\frac{2\pi }{25}) +...+ sin (24\frac{\pi }{25})=cotg\frac{\pi }{25}$

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