just use multiplication rule
f'(x)=e^x(cosx-sinx)
f''(x)=-2 e^x sinx
f'(x)=e^x(cosx-sinx)
f''(x)=-2 e^x sinx
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i would answer but its a pain to write down e^x and cosx so many times
especially when solving for f''(x)
especially when solving for f''(x)