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का S आटे है. oo lm'znA‘Sin 12%sin24°sin48° sin84° = (EAMCET-80)1) c0s20°c0s40°cos60° cos80° B)Sin20° sin40° singQ° शाC)3/15 > D)none |
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Answer» Sin84° sin48° sin24° sin12°= 1/4*(2sin84° sin24°) (2sin48° sin12°)= 1/4*(cos60°- cos108°)(cos36°- cos60°)= 1/4*(1/2 + sin18°) (cos36° - 1/2)= 1/4*(1/2 + (√5 - 1)/4) ((√5 + 1)/4 - 1/2)= 1/4* ((√5 + 1)/4) ((√5 - 1)/4)= 1/64 * (5-1)= 1/16 Formula used: cosA - cosB = 2sin((a+b)/2) sin((a-b)/2)Values of sin18° = (√5 - 1)/4 and cos36° = (√5 + 1)/4 |
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