Miara kąta wewnętrznego $n$ - kąta foremnego wynosi $180^{\circ }\cdot \frac{n-2}{n}$.

Zatem suma miar kątów tego $n$ - kąta wynosi:

$n\cdot 180^{\circ }\cdot \frac{n-2}{n}=180^{\circ }\cdot \left(n-2\right)$

---

a)

$180^{\circ }\cdot \left(n-2\right)=720^{\circ }|:180^{\circ }$

$n-2=4|+2$  

$n=6$

---

b)

$180^{\circ }\cdot \left(n-2\right)=900^{\circ }|:180^{\circ }$

$n-2=5|+2$  

$n=7$

---

c)

$180^{\circ }\cdot \left(n-2\right)=1260^{\circ }|:180^{\circ }$

$n-2=7|+2$  

$n=9$

---

d)

$180^{\circ }\cdot \left(n-2\right)=1440^{\circ }|:180^{\circ }$

$n-2=8|+2$  

$n=10$

---

e)

$180^{\circ }\cdot \left(n-2\right)=1620^{\circ }|:180^{\circ }$

$n-2=9|+2$  

$n=11$