Review the proof of cos(A - B) = cosAcosB + sinAsinB.
Step 1: √(cos A - cosB)² + (sinA - sinB)² = √(cos(A - B) -1)² + (sin(A - B) - 0)²
Step 2: (cos A - cosB)² + (sinA - sinB)² = (cos(A - B) -1)² + (sin(A - B) - 0)²
Step 3: cos²A - 2cosAcosB + cos²B + sin²A - 2sinAsinB + sin²B = cos²(A - B) - 2(cos(A - B)) + 1 + sin²(A - B)
Step 4: ._______ - 2cosAcosB - 2 sinAsinB = _______ - 2cos(A - B) + 1
Step 5: -2 (cosAcosB + sinAsinB = cos(A - B)
Step 6: cosAcosB + sinAsinB = cos(A - B)
which of the following complete step 4 pf the proof ?
O 1 and 1
O 2 and 1
O (cosAcosB)²(sinAsinB)² and (cos²(A - B))(sin²(A - B))
O (cos²A + sin²A)(cos²B + sin²B) and (cos²(A - B))(sin²(A - B))