Suppose $f$ is holomorphic in an open set $U$ and the closure of a disk $D(z_{0},r)$ is contained in $U$, then , $f(z_{0}) = \frac{1}{2 \pi} \int^{2\pi}_{0} f(z_{0} + r e^{it})dt$, which is a version of the statement of the Mean Value Property for Holomorphic functions.
I understand that this is a restatement of The Cauchy Integral Formula for Disks.
How does one show that the MVP for Holomorphic functions holds for $Re(f) = u$ and $Im(f) = v$?