Prove by vector method:sin(A-B)=sinAcosB-cosAsinBsin(A+B)=sinAcosB+cosAsinBcos(A-B)=cosAcosB+sinAsinBcos(A+B)=cosAcosB-sinAsinB
Prove by vector method:
sin(A-B)=sinAcosB-cosAsinB
sin(A+B)=sinAcosB+cosAsinB
cos(A-B)=cosAcosB+sinAsinB
cos(A+B)=cosAcosB-sinAsinB