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If cos A = 3/4 then sin ""(A) /(2 )...

If ` cos A = 3/4 ` then ` sin ""(A) /(2 ) . Sin 5 (A)/(2) ` is

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The correct Answer is:
11
`32sin((A)/(2))sin((5A)/(2))`
`=16(cos((A)/(2)-(5A)/(2))-cos((A)/(2)+(5A)/(2)))`
`=16(cos 2A-cos3A)`
`=16(cos 2A-cos3A)`
`=16(2cos^(2)A-1-4cos^(3)A+3cosA)`
Now, putting the value of `cosA=3//4`, we get
`32sin((A)/(2))sin((5A)/(2))=11`.
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CENGAGE-TRIGONOMETRIC RATIOS AND TRANSFORMATION FORMULAS-Exercise 3.4
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