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प्रश्न
If A = 600 and B = 300, verify that:
(ii) cos (A – B) = cos A cos B + sin A sin B
उत्तर
cos (A – B) = cos 300 =`sqrt(3)/2`
cos A cos B + sin A sin B = cos 600 cos 300 + sin 600 sin 300
=`( 1/2 xx sqrt(3)/2 + sqrt(3)/2 xx1/2) = (sqrt(3)/4 + sqrt(3)/4) = 2 xx sqrt(3)/4 = sqrt(3)/2`
∴ cos (A – B) = cos A cos B + sin A sin B
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