Recognize the integral: Recognize the integral we need to solve.We have the integral of the square root of x times the arc tangent of the square root of x, which is written as:∫x⋅arctan(x)dx
Use integration by parts: Use integration by parts.Integration by parts is given by the formula:∫udv=uv−∫vduWe need to choose u and dv such that du and v are easier to integrate. Let's choose:u=arctan(x) (since its derivative is simpler)dv=xdx (since its antiderivative is straightforward)
Compute du and v: Compute du and v.To find du, we differentiate u with respect to x:du=dxd[arctan(x)]dxUsing the chain rule and the derivative of arctan(x), which is 1+x21, we get:du=21⋅1+x1⋅x1dxNow, to find v, we integrate dv:v=∫xdxv=32⋅x23
Apply integration by parts formula: Apply the integration by parts formula.Now we have all the parts needed to apply the integration by parts formula:∫x⋅arctan(x)dx=uv−∫vdu= arctan(x)⋅32⋅x23−∫32⋅x23⋅21⋅(1+x)1⋅x1dx
Simplify the integral: Simplify the integral.Simplify the expression inside the integral:∫(32)⋅x23⋅(21)⋅(1+x1)⋅(x1)dx= ∫(31)⋅x⋅(1+x1)dxNow we have a simpler integral to solve.
Solve the simplified integral: Solve the simplified integral.To solve ∫31⋅x⋅1+x1dx, we can use a simple substitution:Let t=1+x, then dt=dx and x=t−1.Our integral becomes:∫31⋅(t−1)⋅t1dt=31⋅∫(1−t1)dt=31⋅(t−ln∣t∣)Now we substitute back for x:=31⋅(1+x−ln∣1+x∣)
Write the final answer: Write the final answer.Combining the result from integration by parts with the solved integral, we get:∫x⋅arctan(x)dx=arctan(x)⋅(32)⋅x23−(31)⋅(1+x−ln∣1+x∣)+Cwhere C is the constant of integration.