- #1
swarog46
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Homework Statement
[itex]\int^{2\pi}_0{cos(x)cos(nx)dx}=?,n\in Z[/itex]
Homework Equations
The Attempt at a Solution
I think that this eq has zero solve. However my teacher says that its incorrect.
[itex]cos(x) cos(nx) = 1/2 (cos (x-nx) + cos (x+nx))[/itex]
[itex]\int^{2\pi}_0{cos(x)cos(nx)dx}=\frac{1}{2n}(sin(2 \pi (1-n))+sin(2 \pi (1+n)))[/itex] which gives 0 for n=1, but when i give n=1 before start integrating, then I've got non zero solve.