(sinx+cosx)^2=2 sin^2x+cos^2x+2sinxcosx=2 1+2sinxcsx=2 2sinxcosx=1 sinxcosx=1/2
sin x +cos x =根号2 sinx=根号2-cosx (根号2-cosx)cosx =1/2 -cos^2x+根号2cosx -1/2=0
cos^2x-根号2cosx +1/2=0 (cosx-根号2/2)^2=0 cosx-根号2/2=0 cosx=根号2/2 sinx=根号2-cosx =根号2/2 tanx=sinx/cosx=1
