✔ 最佳答案
sec2x = (2﹣cosx﹣sinx)/(1﹣sinx)
1 + tan2x = (1﹣cosx)/(1﹣sinx) + 1
tan2x = (1﹣cosx)/(1﹣sinx)
(1﹣sinx)(tan2x) = (1﹣cosx)
sin2x﹣sin3x = cos2x﹣cos3x
sin2x﹣cos2x = sin3x﹣cos3x
(sinx+cosx)(sinx﹣cos x) = (sinx﹣cosx)(sin2x + sinxcosx + cos2x)
sinx﹣cosx = 0 or sinx+cosx = 1 + sinxcosx
tanx = 1 or 1+sinxcosx﹣-sinx﹣cosx = 0
tanx = 1 or 1﹣sinx+cosx(sinx﹣1) = 0
tanx=1 or (1﹣cosx)(1﹣sinx)= 0
tanx=1 or sinx = 1 or cosx = 1
x=0o,45o,90o,225o,360o
sec90o is undefined,so x is not 90o
∴x = 0o, 45o, 225o,360o