(tan10°-√3)*cos10°/sin50°=(sin10°-√3cos10°)/sin50°=2(1/2*sin10°-√3/2*cos10°)/sin50°=2(sin10°cos60°cos10°sin60°)/sin50°=2sin(10-60)°/sin50°=2sin(-50)°/sin50°=-2sin50°/sin50°=-2
