Properties of Shape - Angles in a Triangle (1) - Presentation

During a mathematics lesson focused on the properties of shapes, students delve into the topic of angles within triangles. The lesson begins with a discussion prompting learners to identify and describe the properties of at least two out of the four types of triangles: equilateral, isosceles, scalene, and right-angled. Following this, the first activity encourages students to create these triangles using different-coloured pieces of card. They then measure each interior angle with a protractor and observe that, regardless of the triangle type, the total sum of the interior angles is always 180 degrees. This key concept is further reinforced when students tear off the corners of any triangle and rearrange them to form a straight line, visually demonstrating the sum of the angles.

Subsequent activities challenge the students to apply their understanding by calculating missing angles and identifying the type of triangle from which the corners have been torn. They discover that the type of triangle does not affect the sum of its interior angles. Activities include finding missing angles in various triangles and determining if the size of the triangle alters this fundamental rule. The lesson also incorporates reasoning exercises, such as debunking the incorrect claim that a triangle can have two 90-degree angles and solving problems involving scalene triangles with specific angle relationships. The session concludes with independent work where students investigate angles in triangles, calculate missing angles, and validate or refute statements to solidify their comprehension of the topic.