Vector $\overline{M}$ lies in the xy plane making an angle of θ above the positive x-axis. Vector $\overline{N}$ is lying in the same plane making an angle Φ below the positive x-axis. Determine their dot product.
Hint: Use one of the following identities-
cos(A + B) = cosAcosB - sinAsinB
cos(A - B) = cosAcosB + sinAsinB

• A. McosθcosΦ + NsinθsinΦ
• B. McosθcosΦ - NsinθsinΦ
• C. MN(cosθcosΦ - sinθsinΦ)
• D. MN(cosθcosΦ + sinθsinΦ)

Answer: (C)