Given:
Interior angle of a polygon - [tex] 144^{o}
Find:
Number of diagonals the polygon have
Solution:
(Let us settle with the degrees later.)
Interior angle = [tex] \frac{180 (n-2)}{n) [/tex]
144 = [tex] \frac{180 (n-2)}{n} [/tex]
144n = 180 n - 360
144n - 180n = 180n - 180n - 360
[tex] \frac{-36n = -360}{-36} [/tex]
n = 10
n = 10, that means that the polygon is a 10-sided polygon or DECAGON.
The remaining problem is its number of diagonals.
Number of diagonals = [tex] \frac{n(n-3)}{2} [/tex]
= [tex] \frac{ 10(10 - 3)}{2} [/tex]
= [tex] \frac{10 (7)}{2} [/tex]
= [tex] \frac{70}{2} [/tex]
= 35
Answer:
The regular polygon that has an interior angle of 144 degrees has 35 diagonals.