cos(A-B)+cos(A+B+π/2)求详细解答过程
问题描述:
cos(A-B)+cos(A+B+π/2)求详细解答过程
答
cos(A-B)+cos(A+B+π/2)=cos(A-B)+cos(A+B)cosπ/2-sin(A+B)sinπ/2=cos(A-B)-sin(A+B)=cosAcosB+sinAsinB-sinAcosB-sinBcosA=cosA(cosB-sinB)+sinA(sinB-cosB)=(cosB-sinB)(cosA-sinA)=√2(cosπ/4cosB-sinπ/4sinB...