sin7°cos37°-sin83°cos307° 求过程!

问题描述:

sin7°cos37°-sin83°cos307° 求过程!

sin7°cos37°-sin83°cos307°
=sin7°cos37°-sin(90°-7°)cos(270°+37°)
=sin7°cos37°-cos7°sin37°
=sin(7°-37°)
=sin(- 30°)
= - 2分之1