Hello, can someone help me on this one, please? integral from negative pi to pi of cos mx times cos nx dx where m and n are positive integers. I guess the answer is pi if m = n and zero otherwise. Thanks! ZD
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Originally Posted by ZeroDivisor Hello, can someone help me on this one, please? integral from negative pi to pi of cos mx times cos nx dx where m and n are positive integers. I guess the answer is pi if m = n and zero otherwise. Thanks! ZD Use the equality: $\displaystyle \cos(mx)\cos(nx)=\frac{1}{2}[\cos(m+n)x+\cos(m-n)x]$
Thank you curvature!
Originally Posted by curvature Use the equality: $\displaystyle \cos(mx)\cos(nx)=\frac{1}{2}[\cos(m+n)x+\cos(m-n)x]$ Did you mean $\displaystyle \cos(mx)\cos(nx)=\frac{1}{2}[\cos((m+n)x)+\cos((m-n)x)]$ ?
We can use this method to find out the coefficient of cosnx in Fouriee series
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