interior angle of a regular 18-gon.
It is easier to calculate the exterior angle of a regular polygon of n-sides (n-gon) by the relation
exterior angle = 360/n
For a 18-gon, n=18, so exterior angle = 360/18=20 °
The value of each interior angle is therefore the supplement, or
Interior angle = 180-20=160 degrees.
Naming of a 9-gon
A polygon with 9 vertices is called a nonagon (in English) or enneagon (French ennéagone, but the English version is sometimes used)
You had a good start with the correct answer.
Exterior angle of a 15-gon
The exterior angle of a 15-gon can be calculated using the relation given in the first paragraph, namely
Exterior angle = 360/15=24 degrees
Division using multiples of 10 is different than how most of us learned how to divide. <span>The idea of multiple is what number can 10 go into without a remainder. That is easy. Ten ends in a zero. Thus 10 goes into numbers ending in zero. An example is 60. Ten ends in a zero; 60 ends in a zero. It will divide evenly. </span>
3.10
I think, Im very sorry if this is wrong!
