document.write( "Question 1084680: cos(60°+A)+cos(60°-A)-cosA=0 \n" ); document.write( "

Algebra.Com's Answer #698733 by htmentor(1343) $\"\"$ $\"About$

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I assume the problem involves proving the identity. If so, we proceed as follows:
\n" ); document.write( "Using trig identities, we can write cos(60°+A)+cos(60°-A)-cosA as
\n" ); document.write( "cos(60)cos(A) - sin(60)sin(A) + cos(60)cos(A) + sin(60)sin(A) - cos(A)
\n" ); document.write( "The sine terms cancel, and we are left with
\n" ); document.write( "2cos(60)cos(A) - cos(A) -> cos(A)(2cos(60) - 1)
\n" ); document.write( "Since cos(60) = 1/2, 2cos(60) - 1 = 0, and thus the original expression equals zero for all values of A. \n" ); document.write( "

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