咱们约定以下数字均是角度
tan80-4cos10
=cot10-4cos10
=cos10/sin10-4cos10
=(cos10-4sin10cos10)/sin10
=(cos10-2sin20)/sin10
=[cos10-2sin(30-10)]/sin10
=(cos10-2sin30cos10+2cos30sin10)/sin10
=2cos30sin10/sin10
=2cos30
=√3
咱们约定以下数字均是角度
tan80-4cos10
=cot10-4cos10
=cos10/sin10-4cos10
=(cos10-4sin10cos10)/sin10
=(cos10-2sin20)/sin10
=[cos10-2sin(30-10)]/sin10
=(cos10-2sin30cos10+2cos30sin10)/sin10
=2cos30sin10/sin10
=2cos30
=√3