LO To calculate angles in a triangle In

LO: To calculate angles in a triangle

In this lesson, I will be able to:

Try this This triangle has been drawn between two parallel lines. How many of the missing angles can you work out? What parallel line properties did you use? 3

Connect How do you know? 4

Connect Two students are trying to find the two remaining angles in this isosceles triangle. am going to find this blue angle first … I I am going to find this purple angle first … Help each of the students to complete their solutions. Explain your reasoning. 5

Connect Your turn Deduce the value of the marked angles: 6

Independent task Answers I. Draw a bar model for each of the six problems below. II. Find the missing angle using your model. 7

Independent task Answers I. Draw a bar model for each of the six problems below. II. Find the missing angle using your model. 8

Independent task Answers 2) Find the missing angles in the following problems 9

Independent task Answers 3) Decide if the following statements are always, sometimes or never true. a) The sum of the internal angles of three triangles is 540 degrees. Always b) Two internal angles of a triangle will sum to a value less than 90 degrees. Sometimes c) All the internal angles of a triangle are acute d) A triangle contains two right angles. 10 Never Sometimes

Independent task Answers 4) Find the missing angles in the triangle to the right. Both 31 b) Two copies of the same triangle are joined along degrees corresponding edges to make a four-sided shape as shown. i. What are the internal angles of this shape? ii. How many other four-sided shapes could you make in a similar way? iii. What are the internal angles of these shapes? 11

Explore Work out the missing marked angles. 12

Explore Support Work out the missing marked angles. 13 Hint: Start with the middle triangle

Explore 14 Answers