SOLUTION: If sin A sin B = cos A cos B , then cos(A - B ) = ?

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Question 1011265: If sin A sin B = cos A cos B , then cos(A - B ) = ?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
by definition, cos%28A-B%29+=+cos+%28A%29+cos+%28B%29+%2B+sin%28+A%29+sin%28+B%29
so, if sin%28A%29+sin+%28B%29+=+cos+%28A%29+cos+%28B%29, then
cos%28A-B%29+=+cos%28+A%29+cos+%28B%29+%2B+cos+%28A%29+cos+%28B%29
cos%28A-B%29+=2+cos%28+A+%29cos+%28B+%29