√(1-sin20°)/[cos10°-√(1-sin²100°)]180°>100°>90°cos100°0√(1-sin²100°)=-cos100°cos10°-√(1-sin²100°)=cos10°+cos100°=cos10° + cos(90°+10°)=cos10°-sin10°1-sin20°=1-2si...