(2sin5°-cos25°)\(cos65°)=?（ 根号下1-2sin10°cos10°)\(根号下1-cos^2170°-cos350°)=?
问题描述：
(2sin5°-cos25°)\(cos65°)=?（ 根号下1-2sin10°cos10°)\(根号下1-cos^2170°-cos350°)=?
答
(2sin5°-cos25°)\(cos65°)=(2sin5°-cos(30-5)°)\(cos65°)=(2sin5°-(√3/2cos5°+1/2sin5°)\(cos65°)=（3/2sin5°-√3/2cos5°）/(cos65°)=√3（√3/2sin5°-1/2cos5°）/(cos65°)=-√3（sin（30-5））/(c...