sin^4（112.5度）-cos^4（112.5

sin^4（112.5度）-cos^4（112.5度）

1个回答

sin⁴112.5°-cos⁴112.5°=(sin²112.5°+cos²112.5°)(sin²112.5°-cos²112.5°)
=1*[-(cos²112.5°-sin²112.5°)]
=-cos225°
=cos45°
=√2/2