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59°sin 31°13. सिद्ध कीजिए कि-- 25 70°2, 6 —Sin 24 ~8 cos® 60°=0 |
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Answer» Sin(90°-α) = cosαcos(90°-α) = sinα so,cos70°/sin20° + cos59°/sin31° -8 sin²30°=[cos(90°-20)]/sin20° + [cos(90°-31°)]/sin31° - 8×(1/2)²=sin20°/sin20° + sin31°/sin31° - 2= 1+1- 2= 0 |
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