SOLUTION: cos(60�+A)+cos(60�-A)-cosA=0

Question 1084680: cos(60�+A)+cos(60�-A)-cosA=0
Answer by htmentor(1343) (Show Source): You can put this solution on YOUR website!
I assume the problem involves proving the identity. If so, we proceed as follows:
Using trig identities, we can write cos(60�+A)+cos(60�-A)-cosA as
cos(60)cos(A) - sin(60)sin(A) + cos(60)cos(A) + sin(60)sin(A) - cos(A)
The sine terms cancel, and we are left with
2cos(60)cos(A) - cos(A) -> cos(A)(2cos(60) - 1)
Since cos(60) = 1/2, 2cos(60) - 1 = 0, and thus the original expression equals zero for all values of A.
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