Question 17
The figure shows a regular ten-sided polygon with center $O$. What is the measure of angle $a$?
A) $15^\circ$; B) $18^\circ$; C) $20^\circ$; D) $30^\circ$; E) $36^\circ$.
A) $15^\circ$; B) $18^\circ$; C) $20^\circ$; D) $30^\circ$; E) $36^\circ$.