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"Show that : " "cos" pi/11 +"cos"(3pi)/1...

`"Show that : " "cos" pi/11 +"cos"(3pi)/11+ "cos" (5pi)/11+ "cos" (7pi)/11+"cos" (9pi)/11 =1/2`.

Text Solution

Verified by Experts

The correct Answer is:
`= 1/(2 sin theta)[2 sin theta cos theta + 2 cos 3 theta sin theta + 2 cos 5 theta sin theta + 2 cos 7 theta sin theta + cos 9 theta sin theta]`
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