using the concept of the walli's formula find the area bounded by the curve y=sinx and y=cosx from pi/4 to 5pi/4??
http://www.learningace.com/doc/6138186/5b99373c5323a0518f25b611d97ade45/wallis-s-formula-to-integrate-powers-of-sine-or-sine-0-pi-2
is a good place to start. Try adjusting the interval to fit your needs.