Question 69

If cos(A-B) - cos(A+B) = x, then the value of x is

Solution

Expression : cos(A-B) - cos(A+B) = x

= $$(cos Acos B + sin Asin B) - (cos Acos B - sin Asin B)$$

= $$sin Asin B + sin Asin B = 2sin Asin B$$

=> Ans - (A)

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