1. 6.2 Area of a Triangle Mme DiMarco

2.  Learning Goal: use a formula to find the area of a triangle Learning Goal

3.  If you draw a diagonal line across a parallelogram, you will find two congruent triangles!  These two congruent triangles have the same area  Therefore, the area of a triangle is ½ the area of a parallelogram Connect Triangle 1 Triangle 2 Parallelogram

4.  Step 1: draw a congruent triangle on one side of the triangle to make a parallelogram Finding the area of a triangle (method 1) 6cm 5cm Original Triangle 5cm 6cm Parallelogram

5.  Step 2: Solve for area using formula of a parallelogram A = base x height A = 6 x 5 A = 30 cm 2 Finding the area of a triangle (method 1) 5cm 6cm Parallelogram

6.  Step 3: divide the area of the parallelogram by 2 to find the area of the triangle A p = 30 cm 2 Therefore… A t = 30 ÷ 2 A t = 15 cm 2 Area of the triangle is 15 cm 2 Finding the area of a triangle (method 1) 5cm 6cm Parallelogram

7. Alternatively, you can use the formula below to find the area of a triangle A = ½ ( b x h) Finding the area of a triangle (method 2)

8. Use the formula to find the area of the triangle below A = ½ ( b x h) A = ½ (17 x 9) A = ½ (153) A = 76,5 cm 2 Example 17 cm 9 cm

9.  Page 222  Questions #1 - 4, 7, 9 Devoirs