求值：sin(10°+x)cos(50°-x)+sin(50°-x)cos(10°+x)
问题描述：
求值：sin(10°+x)cos(50°-x)+sin(50°-x)cos(10°+x)
答
套公式啊,sin(10°+x)cos(50°-x)+sin(50°-x)cos(10°+x)=sin(10°+x+50°-x)=sin60°=√3/2.诶……那cos呢……sin(A+B)=sinAcosB+cosAsinB。sin(A-B)=sinAcosB-cosAsinB。cos(A+B)=cosAcosB-sinAsinB。cos(A-B)=cosAcosB+sinAsinB。