Forget to write "+ c" after indefinite integral

You wrote sen, instead of sin.
To me it looks like dampened oscillation, just google the formula.

I'm brazilian, sin = sen...

>dampened oscillation

but you saved my day

It was simply f(x) = e^(-x)*cos(2*pi*x)

at least we don't make retarded algebra or calculus mistakes and go fast.

ENSfag btw.