sin^4 112度30分-cos^4 112度30分等于几度
问题描述：
sin^4 112度30分-cos^4 112度30分等于几度
答
(sin112.5°)^4-(cos112.5°)^4
=[(sin112.5°)^2+(cos112.5°)^2]*[(sin112.5°)^2-(cos112.5°)^2]
=(sin112.5°)^2-(cos112.5°)^2
= -[(cos112.5°)^2-(sin112.5°)^2]
= -cos225°
=cos45°
=√2/2 .