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Grade 11Trigonometry

The number of solutions of equation is equal to:
(A) (B) (C) (D)

Profile image of Vikram
6 Years agoGrade 11
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1 Answer

Profile image of Arun
6 Years ago
Dear student
 
On simplicity
 
We get
LHS
 
Cos theta + cos 3 theta +.....cos 17 theta
 
Sin (9 theta)* cos 9theta/sin theta
 
 = Sin18 theta/2sin tgeta = ½
 
Sinn18 theta = sin theta
 
18 theta = nπ + (-1)ⁿ theta
 
Now make case for n off and even

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