Integral of $$$e^{\sin{\left(x \right)}} \cos{\left(x \right)}$$$

Find $$$\int e^{\sin{\left(x \right)}} \cos{\left(x \right)}\, dx$$$.

Let $$$u=\sin{\left(x \right)}$$$.

Then $$$du=\left(\sin{\left(x \right)}\right)^{\prime }dx = \cos{\left(x \right)} dx$$$ (steps can be seen »), and we have that $$$\cos{\left(x \right)} dx = du$$$.

Thus,

$${\color{red}{\int{e^{\sin{\left(x \right)}} \cos{\left(x \right)} d x}}} = {\color{red}{\int{e^{u} d u}}}$$

The integral of the exponential function is $$$\int{e^{u} d u} = e^{u}$$$:

$${\color{red}{\int{e^{u} d u}}} = {\color{red}{e^{u}}}$$

Recall that $$$u=\sin{\left(x \right)}$$$:

$$e^{{\color{red}{u}}} = e^{{\color{red}{\sin{\left(x \right)}}}}$$

Therefore,

$$\int{e^{\sin{\left(x \right)}} \cos{\left(x \right)} d x} = e^{\sin{\left(x \right)}}$$

Add the constant of integration:

$$\int{e^{\sin{\left(x \right)}} \cos{\left(x \right)} d x} = e^{\sin{\left(x \right)}}+C$$

$$$\int e^{\sin{\left(x \right)}} \cos{\left(x \right)}\, dx = e^{\sin{\left(x \right)}} + C$$$A