Product of Trigonometric Ratios in Terms of Their Sum
The value of ...
Question
The value of cosπ22⋅cosπ23⋅...⋅cosπ210⋅sinπ210 is :
A
11024
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B
12
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C
1512
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D
1256
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Solution
The correct option is C1512 A=cosπ22⋅cosπ23⋅...⋅cosπ210⋅sinπ210 Put π210=x⇒π=210x ⇒A=(cosx⋅cos2x⋅...⋅cos28x)sinx As we know sin2nθ2nsinθ=cosθ⋅cos2θ⋅...cos2n−1θ⋅ Here, n−1=8⇒n=9 ⇒A=sin29x29sinx⋅sinx ⇒A=sin29π21029 ⇒A=1512