Use the formula that states that the sum of the angles of an n-sided polygon is given by
S=(n−2)180
0
........(1)
Since we are given that the two angles are right angles and each of the remaining angles is 144
0
, therefore, the sum is:
S=90
0
+90
0
+(n−2)144
0
.........(2)
Therefore setting (2) equal to (1) we get
(n−2)180
0
=90
0
+90
0
+(n−2)144
0
⇒(n−2)180
0
−(n−2)144
0
=180
0
⇒(n−2)(180
0
−144
0
)=180
0
⇒(n−2)(36
0
)=180
0
⇒n−2=
36
180
⇒n−2=5
⇒n=5+2=7
Hence, the polygon has 7 sides.
