interior angle
internal angle

The interior angles of an ideal triangle are all zero.

As a consequence, all its interior angles are less than 180 .

The sum of any icosagon's interior angles is 3240 degrees.

In normal space, the interior angles of a square measure 90 degrees each.

Thus the interior angle at each vertex is either 90 or 270 .

The sum of any triacontagon's interior angles is 5040 degrees.

A regular megagon has an interior angle of 179.99964 .

Now while I finish it off, if you'd like to just measure one of the interior angles that I've already done.

A size of the interior angle of the regular octagon.

What do they mean by the interior angle?