Calculus Examples

$\int e^{x} \cos (x) d x$

Step 1

Reorder $e^{x}$ and $\cos (x)$ .

$\int \cos (x) e^{x} d x$

Step 2

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \cos (x)$ and $d v = e^{x}$ .

$\cos (x) e^{x} - \int e^{x} (- \sin (x)) d x$

Step 3

Since $- 1$ is constant with respect to $x$ , move $- 1$ out of the integral.

$\cos (x) e^{x} - - \int e^{x} (\sin (x)) d x$

Step 4

Simplify the expression.

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Step 4.1

Multiply $- 1$ by $- 1$ .

$\cos (x) e^{x} + 1 \int e^{x} (\sin (x)) d x$

Step 4.2

Multiply $\int e^{x} (\sin (x)) d x$ by $1$ .

$\cos (x) e^{x} + \int e^{x} (\sin (x)) d x$

Step 4.3

Reorder $e^{x}$ and $\sin (x)$ .

$\cos (x) e^{x} + \int \sin (x) e^{x} d x$

Step 5

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \sin (x)$ and $d v = e^{x}$ .

$\cos (x) e^{x} + \sin (x) e^{x} - \int e^{x} \cos (x) d x$

Step 6

Solving for $\int e^{x} \cos (x) d x$ , we find that $\int e^{x} \cos (x) d x$ = $\frac{\cos (x) e^{x} + \sin (x) e^{x}}{2}$ .

$\frac{\cos (x) e^{x} + \sin (x) e^{x}}{2} + C$

Step 7

Rewrite $\frac{\cos (x) e^{x} + \sin (x) e^{x}}{2} + C$ as $\frac{1}{2} (\cos (x) e^{x} + \sin (x) e^{x}) + C$ .

$\frac{1}{2} (\cos (x) e^{x} + \sin (x) e^{x}) + C$