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Prove that sum(r=1)^n(1/(costheta+"cos"(...

Prove that `sum_(r=1)^n(1/(costheta+"cos"(2r+1)theta))=(sinntheta)/(2sintheta costhetacos (n+1)theta),(w h e r en in N)dot`

A

`(sin(n+1)theta)/(sintheta.cosntheta)`

B

`(sinntheta)/(sin2theta.cos(n+1)theta)`

C

`(tan(n+1)theta)/(sin ntheta)`

D

`(sin(n-1)theta)/(sintheta.cosntheta)`

Text Solution

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The correct Answer is:
B
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