- 求三角函数值[(1+cos20°)/2sin20°]–sin10
- [(1+c20°)/2sin20°]–sin10°(cos5°/sin5°-sin5°/cos5°)=
- [(1+cos20°)/2sin20°]–sin10°(cos5°/sin5°-sin5°/cos5°)=[2cos^10/4sin10cos10]-sin10[(cos^5-sin^5)/sin5cos5]
=cos10/2sin10 -sin10(2cos10/sin10)
=cos10/2sin10 -2cos10
=(cos10 -4sin10cos10)/2sin10
=(cos10 -sin20 -sin20)/2sin10
=(cos10-cos70-sin20)/2sin10
=(2sin40sin30 -sin20)/2sin10
=(sin40-sin20)/2sin10
=(2cos30sin10)/2sin10
=(根号3)/2