How do you integrate int 1/(x^2sqrt(16x^2-9))1x216x29 by trigonometric substitution?

1 Answer
Mar 3, 2018

sqrt(16x^2-9)/(9x)+C16x299x+C.

Explanation:

Suppose that, I=int1/(x^2sqrt(16x^2-9))dx=int1/(x^2sqrt{(4x)^2-3^2})dxI=1x216x29dx=1x2(4x)232dx.

We subst. 4x=3secy," so that, "4dx=3secytanydy4x=3secy, so that, 4dx=3secytanydy.

:. I=int1/{(3/4*secy)^2sqrt(9sec^2y-9)}*(3/4*secytany)dy,

=16/9*1/4int1/(sec^2ytany)*secytanydy,

=4/9int1/secydy,

=4/9intcosydy,

=4/9siny,

=4/9sqrt(1-cos^2y),

=4/9sqrt(1-1/sec^2y),

=4/9sqrt{1-1/(4/3*x)^2},

=4/9sqrt{1-9/(16x^2)}.

rArr I=sqrt(16x^2-9)/(9x)+C.