Question:
Tick (✓) the correct answer:
The sum of all interior angles of a regular polygon is 1080°. What is the measure of each of its interior angles?
(a) 135°
(b) 120°
(c) 156°
(d) 144°
Solution:
(a) 135°
$(2 n-4) \times 90=1080$
$(2 n-4)=12$
$2 n=16$
or $n=8$
Each interior angle $=180-\frac{360}{n}=180-\frac{360}{8}=180-45=135^{\circ}$