cos43°cos77°+sin43°cos167°=?

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/29 07:24:09
cos43°cos77°+sin43°cos167°=?

cos43°cos77°+sin43°cos167°=?
cos43°cos77°+sin43°cos167°=?

cos43°cos77°+sin43°cos167°=?
解答:
cos43°cos77°+sin43°cos167°
= cos43°cos77°-sin43°sin77°
=cos(43°+77°)
=cos120°
=-1/2

cos43°cos77°+sin43°cos167°
=cos43°cos(90-13)°+sin43°cos(180-13)°
=cos43°sin13°-sin43°cos13°
=sin(43-13)°
=sin30°
=1/2

原式=cos43°cos77°+sin43°cos167°=cos43°cos77°+sin43°sin(90°-167°)
=cos43°cos77°-sin43°sin77°=cos(43°+77°)=cos120°=-1/2

原式=cos43cos77-sin43sin77=cos(43+77)=-1/2