prove that P=VI where V=5sinwt and I=10sin(wt-x) and p=25(cosx-cos(2wt-x))

am I correct so far and where do I go from here?

Let wt=A and x=B

P=(5sinA)(10sin(a-b))

P=50(sinA)(sinAcosB-cosAsinB)

P=50(sin^2AcosB-sinAsinBcosA)

P=50(cosB+(sin^2AcosB-sinAsinBcosA-cos^2AcosB))

P=25(cosB-(2sinAsinBcosA+cosBcos^2A-sin^2AcosB))

P=25(cosB-cos(2A-B))