If $a \; =\; cos \; 2\alpha \; + \; i \; sin \; 2\alpha , \; b \; =\; cos\; 2\beta + i\; sin\; 2\beta\;$ and $\;c\; = \; cos \; 2\gamma\; + \; i sin\; 2\gamma$ prove that $\sqrt{abc}\; + \; \frac{1}{\sqrt{abc}}\; = \; 2\; cos\left ( \alpha \;+\;\beta \;+\;\gamma \right )$

Question

where m, n ∈ N.

This is the first part of the multi-part Q10.