Question

cos80°cos35°+cos10°cos55°的值为(    )

A.               B.             C.        D.

Answer 1

解析：cos80°cos35°+cos10°cos55°=cos80°cos35°+cos(90°-80°)cos(90°-35°)

=cos80°cos35°+sin80°sin35°=cos(80°-35°)=cos45°=.

答案：A