What is the integral of 4/(x^2+y^2) ?

The integral of 4/(x^2+y^2) is 4/y arctan(x/y)+C

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integral of 4/(x^2+y^2)

\int \frac{4}{x ^{2} + y ^{2}} d x

\frac{4}{y} arctan (\frac{x}{y}) + C

Solution steps

\int \frac{4}{x ^{2} + y ^{2}} d x

Take the constant out:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= 4 \cdot \int \frac{1}{y ^{2} + x ^{2}} d x

Apply Integral Substitution

= 4 \cdot \int \frac{1}{y ( u ^{2} + 1 )} d u

Take the constant out:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= 4 \cdot \frac{1}{y} \cdot \int \frac{1}{u ^{2} + 1} d u

Use the common integral:

\int \frac{1}{u ^{2} + 1} d u = arctan (u)

= 4 \cdot \frac{1}{y} arctan (u)

Substitute back

u = \frac{x}{y}

= 4 \cdot \frac{1}{y} arctan (\frac{x}{y})

Simplify

4 \cdot \frac{1}{y} arctan (\frac{x}{y}) : \frac{4}{y} arctan (\frac{x}{y})

= \frac{4}{y} arctan (\frac{x}{y})

Add a constant to the solution

= \frac{4}{y} arctan (\frac{x}{y}) + C

What is the integral of 4/(x^2+y^2) ?
The integral of 4/(x^2+y^2) is 4/y arctan(x/y)+C