Worksheet Chapter 9: Basic Polygons

1. The interior angles of a quadrilateral are given as x°, (x + 20)°, 2x°, and 80°. Calculate the value of x.

2. True or False: The sum of the interior angles of a triangle is always 180 degrees.

3. In a parallelogram ABCD, angle A = (3x - 10)° and angle C (opposite angle to A) = (x + 50)°. Calculate the value of x and find all 4 interior angles of the parallelogram.

4. A polygon has 14 diagonals. Using the diagonal formula, find the number of sides this polygon has and name the polygon.

5. Calculate the number of diagonals in a polygon with 10 sides (decagon).

6. Which quadrilateral has all sides equal in length and diagonals that bisect each other at right angles?

7. True or False: A kite has 2 lines of symmetry.

8. An exterior angle of a triangle is 130°. If one of the opposite interior angles is twice the other opposite interior angle, find the measure of both interior angles.

9. Fill in the blank: A polygon with 8 sides is called an ________.

10. In an isosceles triangle, the vertex angle measures 50°. Find the value of each base angle.