If a + 2 b cos x ) ( a - 2 b cos y = a 2 - b 2 , where a b 0 , then d x d y at π 4 , π 4 is:

Question

If a + 2 b cos x ) ( a - 2 b cos y = a 2 - b 2 , where a > b > 0 , then d x d y at π 4 , π 4 is:, a - 2 b a + 2 b, a - b a + b, a + b a - b, 2 a + b 2 a - b

MARKS App · Accepted Answer

a + 2 b cos x a − 2 b cos y = a 2 − b 2 a − 2 b cos y − 2 b sin x d x d y + 2 b sin y a + 2 b cos x = 0 d x d y = 2 b sin y a + 2 b cos x 2 b sin x a − 2 b cos y = sin y a + 2 b cos x sin x a − 2 b cos y d x d y π 4 , π 4 = a + b a − b .

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