Review the proof of cos(A - B) = cosAcosB + sinAsinB.

Step 1: StartRoot (cosine A minus cosine B) squared + (sine A minus sine B) squared EndRoot = StartRoot (cosine (A minus B) minus 1) squared + (sine A (A minus B) minus 0) squared EndRoot

Step 2: (Cosine A minus cosine B) squared + (sine A minus sine B) squared = (cosine (A minus B) minus 1) squared + (sine (A minus B) minus 0) squared

Step 3:

Step 4:

Step 5:


Step 6:
Cosine A cosine B + sine A sine B = cosine (A minus B)

Step 7:
Cosine (A minus B) = cosine A cosine B + sine A sine B

Which of the following complete step 4 of the proof?

1 and 1
2 and 1
(cosAcosB)2(sinAsinB)2 and (cos2(A – B))((sin2(A – B))
(cos2A + sin2A)(cos2B + sin2B) and (cos2(A – B))(sin2(A – B))