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Given that `(1+sqrt(1+x))tany=1+sqrt(1-x)`. Then `sin4y`is equal to`4x`(b) `2x`(c) `x`(d) none of theseA. 4xB. 2xC. xD. none of these. |
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Answer» Correct Answer - C `tan y=(1+sqrt(1-x))/(1+sqrt(1+x))` Let `x=cos theta,` then `sqrt(1-x)=sqrt(2)sin(theta//2),sqrt(1+x)=sqrt(2)cos(theta//2)` `rArr tany=(sqrt(2)[(1)/sqrt(2)+sin((theta)/(2))])/(sqrt(2)[(1)/sqrt(2)+cos((theta)/(2))])``=(sin((pi)/(4))+sin((theta)/(2)))/(cos((pi)/(4))+cos((theta)/(2)))` `=(2sin((pi)/(8)+(theta)/(4))cos((pi)/(8)-(theta)/(4)))/(2cos((pi)/(8)+(theta)/(2))cos((pi)/(8)-(theta)/(4)))` `=tan((pi)/(8)+(theta)/(4))` |
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