Answer:
Step-by-step explanation:
Consider the triangle (<em>in </em><em>which </em><em>angle</em><em>4</em><em> </em><em>is </em><em>present</em>)
by angle sum property,
20 + 40 + angle4 = 180
60 + angle4 = 180
angle4 = 180 - 60
angle4 = 120
Also,
angle2 = 120 (vertically opposite angles)
angle1 + angle2 = 180 (linear pair)
angle1 + 120 = 180
angle1 = 180 - 120
angle1 = 60
To find the sum of the interior angles of a nonagon, divide it up into triangles... There are seven triangles... Because the sum of the angles of each triangle is 180 degrees... We get
7 * 180 = 1260°
So, the sum of the interior angles of a nonagon is 1260 degrees.
