Question Number 78815 by mathocean1 last updated on 20/Jan/20
$$\mathrm{show}\:\mathrm{that} \\ $$$$\mathrm{sin}\frac{\mathrm{2}\pi}{\mathrm{5}}=\mathrm{sin}\frac{\mathrm{3}\pi}{\mathrm{5}} \\ $$
Answered by mind is power last updated on 20/Jan/20
$$\frac{\mathrm{3}\pi}{\mathrm{5}}=\pi−\frac{\mathrm{2}\pi}{\mathrm{5}}\:\:\: \\ $$