How do I find the minimum degree sum?

Question

A simple graph has 5 vertices all with the same degree and is also Eulerian.

Answer 1

sum of the 5 interior angles of a regular pentagon = 540 degrees

each interior angle = 540/5 = 108 degrees

5 x 108 = 540 degrees

general formula is (n-2)180 = sum of interior angles of an n sided polygon

for any triangle, sum of interior angles = 180

for a quadralateral, 360

for pentagon 540

for hexagon 720

heptagon 900

octagon 1180

9 sided polygon 1260

10 sided 1440

n sided (n-2)180= 180n-360