Let f be continuous , and strictly monotonic increasing, on [0, a ] Let `g=f^(-1)` . If `f (0)=0,0 <=w<=a , 0<=h<= f(a)` , prove that `int_0^wf+int_0^hg>=wh` . Hence evaluate `int_0^(pi/2)sin xdx int_0^1sin^(-1) xdx`