Geometry formulas for area and perimeter of shapes

Octagon

Octagon
$$\textbf{Area of the octagon}$$
$$A = \frac{1}{4} · 8 · b^2 · \frac{\cos\big(\frac{\pi}{8}\big)}{\sin\big(\frac{\pi}{8}\big)} $$Calcular
$$\textbf{Perimeter of the octagon}$$
$$P = 8 · b $$Calcular