Evaluate: `intsqrt(9-x^2)dx`

Explanation

`intcosx sqrt(4-sin^(2) x) dx`
` =int sqrt(4^(2) -t^(2)) dt " "Let sin x =t`
`rArr cos x dx =dt`
`=int sqrt(2^(2)-t^(2)) + (2^(2))/(2) sin^(-1) ((t)/(2))+c`
` =(sin x)/(2) sqrt(4-sin^(2)) x+ 2sin^(-1) ((sinx)/(2))+c`