3.4 CALCULATING ANGLES IN TRIANGLES & QUADRILATERALS 

Learning objectives

At  the end of this paragraph you are able to...

...recognize an isosceles triangle.

...recognize a right-angled triangle. 

...calculate angles in special triangles. 

...use the sum of the angles of a triangle to calculate angles.

...use the sum of the angles of a quadrilateral to calculate angles.

Explanation videos

Special triangles

Learn about isosceles triangles, equilateral triangles, right-angled triangles and isosceles right-angled triangles

Sum of the angles in a triangle 

Learn about the improper prove of the angle sum of a triangle. You will also see how to calculate with this information.

Making a sketch 

Learn about calculating angles in triangles when making a sketch first. Making a sketch will help you to discover which rules you can use to solve the question.

The sum of the angles in a quadrilateral

Learn about the angle sum of a quadrilateral and the use of it. There will be an example question shown. 

Exercises

Part 1

The exercises in the book: Numbers and space. Page 115 and 117

Do exercise 33, 34, 38, 39, 40, 41 

Part 2

The exercises in the book: Numbers and space. Page 118, 119 and 220

Do exercise 

HAVO: 44, 45, 48, 51, 55

VWO: 45, 47, 49, 52, 58