设sina=tt+t^2=1t^2+t-1=0delta=1+4=5t1=-1+√5/2t2=-1-√5/2(舍)sina=√5-1/2cos^2A+cos^6A =sinA+sin^3A =sinA+sinA(1-sinA) =sinA+sinA-(sinA)^2 =2sinA-sin^2A =2sinA-(1-sinA) =3sinA-1=3*√5-1/2-1=3√5-5/2...