$\int e^{a x} \cos b x d x$ is equal to
Answer & explanation
Correct answer: option 1
Let $I=\int e^{a x} \cos b x d x$
= real part of $\int e^{a x} e^{i b x} d x$
= real part of $\int e^{(a+i b) x} d x$
Hence (1) is the correct answer.
$\int e^{a x} \cos b x d x$ is equal to
Correct answer: option 1
Let $I=\int e^{a x} \cos b x d x$
= real part of $\int e^{a x} e^{i b x} d x$
= real part of $\int e^{(a+i b) x} d x$
Hence (1) is the correct answer.