csx與cosx的關係

(sinx+cosx)^2=2 sin^2x+cos^2x+2sinxcosx=2 1+2sinxcsx=2 2sinxcosx=1 sinxcosx=1/2

sin x +cos x =根號2 sinx=根號2-cosx (根號2-cosx)cosx =1/2 -cos^2x+根號2cosx -1/2=0

cos^2x-根號2cosx +1/2=0 (cosx-根號2/2)^2=0 cosx-根號2/2=0 cosx=根號2/2 sinx=根號2-cosx =根號2/2 tanx=sinx/cosx=1