Recall that fisan odd function iff(-x)=-f(x), and fisan even function iff(-x)=f(x).(a) Let fbean odd function and a>0. Use the u-substitution u=-xto prove that-a0f(x)dx=-0af(x)dx(b) Let fbean odd function and a>0. Prove that-aaf(x)dx=0(c) Using a similar argument, prove that iffisan even function and a>0, then-aaf(x)dx=2(0af(x)dx)