Tuesday, September 2, 2014

int sqrt(x)arctan(x^(3/2)) dx Use integration tables to find the indefinite integral.

For the given integral problem: int sqrt(x)arctan(x^(3/2))dx , we can evaluate this applying indefinite integral formula: int f(x) dx = F(x) +C .
where:
f(x) as the integrand function
F(x) as the antiderivative of f(x)
C as the constant of integration.
From the basic indefinite integration table, the  problem resembles one of the formula for integral of inverse trigonometric function: 
int arctan(u) du = u * arctan(u)- ln(u^2+1)/2+C
For easier comparison, we may apply u-substitution by letting: 
u =x^(3/2 )
To determine the derivative of u, we apply the Power rule for derivative:d/(dx) x^n = n*x^(n-1) dx.
du =d/(dx) x^(3/2)
       = (3/2) *x^(3/2-1) * 1 dx
       = 3/2x^(1/2) dx
       =3/2sqrt(x) dx
Rearrange du =3/2sqrt(x) dx into (2du)/3 = sqrt(x) dx .
Plug-in the values u = x^3/2 and (2du)/3 = sqrt(x) dx , we get:
int sqrt(x)arctan(x^(3/2))dx =int arctan(x^(3/2))*sqrt(x)dx
                                             = int arctan(u) *(2du)/3
Apply the basic integration property: int c*f(x) dx = c int f(x) dx .
int arctan(u) *(2du)/3 =2/3int arctan(u)du.
Applying the aforementioned formula for inverse trigonometric function, we get:
2/3int arctan(u)du=(2/3) *[u * arctan(u)- ln(u^2+1)/2]+C
                                    =(2u * arctan(u))/3- (2ln(u^2+1))/6+C
                                    =(2u * arctan(u))/3- ln(u^2+1)/3+C
Plug-in u =x^(3/2) on (2u * arctan(u))/3- ln(u^2+1)/3+C , we get the indefinite integral as:
int sqrt(x)arctan(x^(3/2))dx =(2x^(3/2) * arctan(x^(3/2)))/3- ln((x^(3/2))^2+1)/3+C
                             =(2x^(3/2) * arctan(x^(3/2)))/3- ln(x^3+1)/3+C
                       or  (2xsqrt(x) arctan(xsqrt(x)))/3- ln(x^3+1)/3+C
 
Note: x^(3/2) = xsqrt(x)

No comments:

Post a Comment

Why is the fact that the Americans are helping the Russians important?

In the late author Tom Clancy’s first novel, The Hunt for Red October, the assistance rendered to the Russians by the United States is impor...