cos2165°+sin215°+cos105°cos15°的值等于()A.B.C.D.

Question

cos ² 165°+sin ² 15°+cos105°cos15°的值等于(    )

A.                 B.                  C.                   D.

cos ² 165°+sin ² 15°+cos105°cos15°的值等于(    )

A.                 B.                  C.                   D.

^{2 2}

A.                 B.                  C.                   D.

Answer 1

解析:原式=cos2(180°-15°)+sin215°+cos(90°+15°)cos15°=cos215°+sin215°-sin15°cos15°=1-sin30°=.答案:D

解析:原式=cos2(180°-15°)+sin215°+cos(90°+15°)cos15°=cos215°+sin215°-sin15°cos15°=1-sin30°=.答案:D

解析:原式=cos2(180°-15°)+sin215°+cos(90°+15°)cos15°=cos215°+sin215°-sin15°cos15°=1-sin30°=.答案:D