$4\mathrm{.}3.$ Trigonometric and Hyperbolic Substitutions. Using an appropriate trigonometric or hyperbolic substitution, find the indefinite integrals of the following functions:

$($a$)\sqrt[\phantom{2}]{1+4x^2}$

$($b$)\sqrt[\phantom{2}]{4-x^2}$

$($c$)\frac{1}{(x^2-1{)}^{\frac{3}{2}}}$

can you do part a using the substitution x$=2$sinht