已知tan(x+π4)=-2,则sin2x-cos2x=题目应是 已知tan(x+π/4)=-2,则sin2x-cos2x=
2020-02-07
已知tan(x+π4)=-2,则sin2x-cos2x=
题目应是 已知tan(x+π/4)=-2,则sin2x-cos2x=
优质解答
tan(x+π4)=-2
(tanx +1)/(1-tanx) =-2
tanx+1 =-2+2tanx
tanx=3
sin2x-cos2x
=2sinxcosx- ((cosx)^2-(sinx)^2)
=2(3/10)-(1/10-3/10)
=4/5
tan(x+π4)=-2
(tanx +1)/(1-tanx) =-2
tanx+1 =-2+2tanx
tanx=3
sin2x-cos2x
=2sinxcosx- ((cosx)^2-(sinx)^2)
=2(3/10)-(1/10-3/10)
=4/5