chứng minh sinx+sin2x/1+cosx+cos2x=tanx Help me :'(

Ta có:

`VT={sinx+sin2x}/{1+cosx+cos2x}`
`=(sinx + 2sinxcosx)/{1+cosx+(2cos^2 x- 1)}`
`=(sinx + 2sinxcosx)/(cosx+2cos^2x)`
`={sinx(1 + 2cosx)}/{cosx(1+2cosx)}`
`={sinx}/{cosx}`
`=tanx=VP`

Vậy `{sinx+sin2x}/{1+cosx+cos2x}=tanx`