sin=1-sin^2 = cos^2cos^2+cos^6 = sin+sin^3= sin+sin(1-cos^2)= sin+sin(1-sin)= sin +sin - sin^2= 2sin - (1-cos^2)= 2sin - (1-sin)= 3sin -1sin^2+sin-1=0 sin=(根号5-1)/2于是.