Question

Dik.cos(A-B)=8/9 dan cos A cos B =2/3. nilai tangen A tangen B =..

Answer 1

Cos(A-B) = cos A cos B + sin A sin B
8/9 = cos A cos B + sin A sin B
8/9 = 2/3 + sin A sin B
8/9 - 2/3 = sin A sin B
8/9 - 6/9 = sin A sin B
2/9 = sin A sin B


tan A tan B = sin A/cos A . sin B/cos B
                 = sin A sin B/cos A cos B = 2/9 / 2/3 = 2/9 . 3/2 = 6/18 = 1/3 (c)

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