若3SinX=CosX,则Cos2X+Sin2X等于?_其他解答

若3SinX=CosX,则Cos2X+Sin2X等于?

人气：116 ℃　时间：2020-02-05 19:41:37

解答

sin^2x+cos^2x=1
sin^2x+9sin^2x=1
sin^2x=1/10
Cos2X+Sin2X
=cos^2x-sin^2x+2sinxcosx
=9sin^2x-sin^2x+6sin^2x
=14sin^2x
=7/5