int sqrt((a+x)/(a-x))dx?

3 Answers
Jun 6, 2017

x + c

Explanation:

int sqrt((a+x)/(a-x)) dx is to be integrated ,so lets rationalize it.

int sqrt((a+x)/(a-x) x sqrt((a-x)/(a+x)) dx

=int sqrt( a^2-x^2)/sqrt(a^2-x^2) dx=int 1 dx= x+c

Jun 6, 2017

a*arc sin(x/a)-sqrt(a^2-x^2)+C.

Explanation:

Let, I=intsqrt((a+x)/(a-x)) dx.

Rationalising, we have,

I=intsqrt((a+x)/(a-x))xx sqrt((a+x)/(a+x)) dx

=int(a+x)/sqrt(a^2-x^2) dx

=aint1/sqrt(a^2-x^2) dx -1/2int(-2x)/sqrt(a^2-x^2) dx

=a*arc sin(x/a)-1/2int{d/dx(a^2-x^2)*(a^2-x^2)^(-1/2)} dx

=a*arc sin(x/a)-1/2(a^2-x^2)^(-1/2+1)/(-1/2+1)

=a*arc sin(x/a)-(a^2-x^2)^(1/2)

rArr I=a*arc sin(x/a)-sqrt(a^2-x^2)+C.

Note that, the later integral has been derived using the following

useful Result

Result : int[f(x)]^n*f'(x)dx=[f(x)]^(n+1)/(n+1)+c, n!=-1.

Enjoy Maths.!

Jun 8, 2017

-a*arc cos(x/a)-sqrt(a^2-x^2)+C.

Explanation:

As an Aliter, let us solve this using a Trgo. Substn.

x=acos 2y rArr dx=-2asin 2ydy.

Also, sqrt{(a+x)/(a-x)}=sqrt{(a+acos2y)/(a-acos2y)}=coty.

:. I=int (cot y)(-2asin 2y)dy.

=-2aint2cos^2ydy

=-2aint(1+cos2y)dy

=-2a(y+sin(2y)/2)

=-a(2y)-asin2y

=-a(2y)-sqrt(a^2-a^2cos^2 2y)

rArr I=-a*arc cos(x/a)-sqrt(a^2-x^2)+C.

Enjoy Maths.!