2sin^β-sinβcosβ
=(2sin^β-sinβcosβ)/1
=(2sin^β-sinβcosβ)/(sin^β+cos^β)分子分母同时除以cos^β
=(2sin^β/cos^β-sinβcosβ/cos^β)/(sin^β/cos^β+cos^β/cos^β)
=(2tg^β-tgβ)/(tg^β+1)
=[2*(-2)^2-(2)]/[(-2)^2+1]
=(8+2)/(4+1)
=10/5
=2