Q#$3$ continued

$0$

$($c$){\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{\sqrt[\phantom{2}]{x^2-a^2}}{x^4}dx,a=$ constant $>0$

$($d$){\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{dx}{1-cosx}($Use the substitution $t=tan(\frac{x}{2}))$