1.

If A,B,C,D are four angles then sin (A-B) cos (A+B) + sin B (B-C) .cos (B+C) + sin (C-D) cos (C+D)+ sin (D-A) cos (D+A)=

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`4 SIN A.sinB sin C sin D`
`4 COS A cos B cos C cos D`

ANSWER :A


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