已知sin(a+135°)=5/13,cos(45°-β ),且-45°cos(45°-β )=3/5
问题描述:
已知sin(a+135°)=5/13,cos(45°-β ),且-45°
cos(45°-β )=3/5
答
cos2(a-β)=2cos^2(a-β)-1
-45°