1+根号3cot20=1+cot30cot20
=(sin30sin20+cos30cos20/(sin30sin20)
=cos10/(sin30sin20)
sin10(1+根号3cot20)
=2sin10cos10/sin20
=sin20/sin20
=1
1+根号3cot20=1+cot30cot20
=(sin30sin20+cos30cos20/(sin30sin20)
=cos10/(sin30sin20)
sin10(1+根号3cot20)
=2sin10cos10/sin20
=sin20/sin20
=1