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 $\frac{a^{2}b^{2}+c^{2}}{abc}\; = \; 2\; cos \; 2\left ( \alpha \;+\;\beta \;+\;\gamma \right )$

Question

where m, n ∈ N.

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