证明:
cos(A-B)-sin(A+B)=cosAcosB+sinAsinB-sinAcosB-cosAsinB
=(cosAcosB-cosAsinB)+(sinAsinB-sinAcosB)
=cosA(cosB-sinB)+sinA(sinB-cosB)
=cosA(cosB-sinB)-sinA(cosB-sinB)
=(cosA-sinA)(cosB-sinB)
证明:
cos(A-B)-sin(A+B)=cosAcosB+sinAsinB-sinAcosB-cosAsinB
=(cosAcosB-cosAsinB)+(sinAsinB-sinAcosB)
=cosA(cosB-sinB)+sinA(sinB-cosB)
=cosA(cosB-sinB)-sinA(cosB-sinB)
=(cosA-sinA)(cosB-sinB)