问题 选择题
sin7°cos37°-sin83°cos53°的值为(  )
A.-
1
2
B.
1
2
C.
3
2
D.-
3
2
答案

sin7°cos37°-sin83°cos53°

=cos83°cos37°-sin83°sin37°

=cos(83°+37°)

=cos120°

=-

1
2

故选A.

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