A triangle is any closed 2D shape with 3 sides and a quadrilateral is any closed 2D shape with 4 sides. The following exercise helps us consider their angles.

Exercise

1.) Draw 4 triangles in your book, labelling the vertices as A, B and C. Try to make them as different from each-other as you can.

2.) Measure the angles BAC, ABC and BCA in each of your triangles.

3.) Calculate BAC + ABC + BCA for each of the triangles. What do you notice?

4.) Draw 4 quadrilaterals in your book, labelling the vertices as A, B, C and D. Try to make them as different from each-other as you can.

5.) Measure the four different angles in each of your quadrilaterals.

6.) For each quadrilateral, add these four angles together. What do you notice?

Knowing that the sum of angles in every triangle is 180º and that the sum of angles in every quadrilateral is 360º let’s us tackle a wide range of questions.

Worked Example

Calculate the angle x in the triangle XYZ below:

Exercise

Answers