Can anyone explain why (cos(x))^2 = (1+cos(2x))/2 ?
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Mar 7, 2007 #2 ziad1985 236 0 cos(x)=(Exp(ix)+Exp(-ix))/2 right? do u know this formula? square before and after the '=' then simplify it..
cos(x)=(Exp(ix)+Exp(-ix))/2 right? do u know this formula? square before and after the '=' then simplify it..
Mar 7, 2007 #3 HallsofIvy Science Advisor Homework Helper 41,808 933 If you don't want to use complex numbers, remember that cos2x= cos^{2} x- sin^{2} x so that the right hand side is (1+ cos^{2} x- sin^{2}x)/2. Do you see an "obvious" way to simplify 1+ cos^{2} x- sin^{2}x?
If you don't want to use complex numbers, remember that cos2x= cos^{2} x- sin^{2} x so that the right hand side is (1+ cos^{2} x- sin^{2}x)/2. Do you see an "obvious" way to simplify 1+ cos^{2} x- sin^{2}x?