(cos^2 10°-cos^2 80°)+sin^2 20°

来源：学生作业帮助网编辑：六六作业网时间：2024/05/30 15:15:32

(cos^210°-cos^280°)+sin^220°(cos^210°-cos^280°)+sin^220°(cos^210°-cos^280°)+sin^220°(cos^210°-cos^28

(cos^2 10°-cos^2 80°)+sin^2 20°
(cos^2 10°-cos^2 80°)+sin^2 20°

(cos^2 10°-cos^2 80°)+sin^2 20°
(cos^2 10°-cos^2 80°)²+sin^2 20°
=(cos^2 10°-sin^2 10°)²+sin^2 20°
=cos²20＋sin²20°
=1