Heptagon
$$\textbf{Area of the heptagon}$$
$$A = \frac{1}{4} · 7 · b^2 · \frac{\cos\big(\frac{\pi}{7}\big)}{\sin\big(\frac{\pi}{7}\big)} $$
$$\textbf{Perimeter of the heptagon}$$
$$P = 7 · b $$