tan(X+45度）=1/3,(sinX-cosX)^2/cos2x?A.3B.-3C.2D.-2

tan(X+45度）=1/3,(sinX-cosX)^2/cos2x?A.3B.-3C.2D.-2
tan(X+45度）=1/3,(sinX-cosX)^2/cos2x?
A.3
B.-3
C.2
D.-2

tan(X+45度）=1/3,(sinX-cosX)^2/cos2x?A.3B.-3C.2D.-2
(sinx-cosx)^2/cos2x
=(sinx-cosx)/(cos^2x-sin^2x)
=(sinx-cosx)/(sinx+cosx)
=(tanx-1)/(1+tanx)
=tan（x-45°）=1/3

tan(x+45)=(tanx+1)/(1-tanx)=1/3
可得tanx