令x=2sint则：cost=√(1-(x/2)²)x=2costdt原式=2∫(cos²t/sint)dt=2∫(1/sint-sint)dt=2∫d[ln|csct-cott|+cost]=2[ln|csct-cott|+cost]+C=2ln|1/√(1-(x/2)²)-√(4-x²)/x|+√(4-x²)+C
