定积分∫√（cosx-cos^3xdx）上面二分

2个回答

=∫(-π/2,π/2)√cosx*|sinx| dx (被积函数为偶函数）
=2∫(0,π/2)√cosx*sinx dx
=-2∫(0,π/2)√cosxdcosx
=(-4/3)(cosx)^(3/2)|(0,π/2)
=4/3