PLANE GEOMETRY(POLYGONS)

A polygon is a closed figure where the sides are all line segments. Each side must intersect exactly two others sides but only at their endpoints. The sides must be noncollinear and have a common end point.
A polygon is usually named after how many sides it has, a polygon with n-sides is called a n-gon. E.g. the building which houses United States Department of Defense is called pentagon since it has 5 sides.
Sides      Polygon
3            triangle
4            quadrilateral
5            pentagon
6            hexagon
7            heptagon
9            nonagon
10         decagon
A regular polygon is a polygon in which all sides are congruent and all the angles are congruent.

TRIANGLE

Interior angles of a triangle is equal to 180°. Interior angles refers to the angles with a particular polygon or shape.And the exterior angles of a triangle sum up to 360°. And exterior angles simpl
Refers to angles outside a figure or shape.

INTERIOR ANGLES OF A TRIANGLE

Let's solve the following examples
1. Find a.

SOLUTION 

Since interior angles of a triangle sum up to 180°,you will equate the sum of the angles on the triangle to 180°.
a+36°+57°=180°
a + 93°=180°
a=180° - 93°
a=87°

2. Find x.

SOLUTION 

Since interior angles of a triangle sum up to 180°,you will equate the sum of the angles on the triangle to 180°.
x+80°+45°=180°
x+ 125°=180°
x=180° - 125°
x=55°

END OF LESSON EXERCISE 

 Solve for the following variables

1.                                 

 

2.

      

3.

4.