(1)sinx+2cosx/3cosx-4sinx
=(tanx+2)/(3-4tanx) (分子分母同时除以cosx得到)
=(2+2)/(3-4×2)
=-4/5
(2)1/2sinxcosx
=(sin²x+cos²x)/2sinxcosx
=(tan²x+1)/2tanx (分子分母同时除以cos²x得到)
=(2²+1)/(2×2)
=5/4
(1)sinx+2cosx/3cosx-4sinx
=(tanx+2)/(3-4tanx) (分子分母同时除以cosx得到)
=(2+2)/(3-4×2)
=-4/5
(2)1/2sinxcosx
=(sin²x+cos²x)/2sinxcosx
=(tan²x+1)/2tanx (分子分母同时除以cos²x得到)
=(2²+1)/(2×2)
=5/4