tanα=2,sin²α-2sinαcosα+2=?

tanα=2,sin²α-2sinαcosα+2=?
tanα=2,sin²α-2sinαcosα+2=?

tanα=2,sin²α-2sinαcosα+2=?
sin²α-2sinαcosα+2
=(sin²α-2sinαcosα)/(sin²α+cos²α)+2
分子分母同时除以cos²α
=(tan²α-2tanα)/(tan²α+1)+2
=0+2
=2