原式=[ 2sin50°+sin10°(1＋√3·tan10°)]√2cos10°=2√2sin50°cos10°+√2 sin10°cos10°+√6 sin^210°=2√2sin50°cos10°+√2/2 sin20°+√6/2(1-cos20°)=2√2sin50°cos10°+√2/2 sin20°-√6/2cos20°+...sin^2(80)怎么变成cos10了sin80=sin(90-10)=cos10√sin^2(80)=cos10