Ashwin Muralidharan IIT MadrasApproved Tutor Answer14 Years agoHi Suhas, MAke the sub sinx = t^2, so that cosxdx = 2tdt. And cos^4x = (1-sin^2 x)^2 = (1-t^4)^2 So that the integral becomes ∫[(1-t^4)^2]2t^2dt. Open the brackets. Directly integrable. Hope it helps. Best Regards, Ashwin (IIT MadraS).