3. (25 Points). Use a trigonometric substitution to evaluate the following integrals. If the integral is indefinite then the final result must be given in terms of x. (a) /22 - 9 dx 24 (b) dx Vx2 + 2 ( c ) x2 + 4dx O (d) x2 + 1dx (Note: For part (d) you may use without proof the result S sec'(x) dx = = (sec x tan x + In | sec x + tan x]) + C which was derived in section 7.2)