1. The Area Of A Triangle. AoAo BoBo CoCo a b c

2. Finding The Formula. Consider the triangle below: AoAo BoBo CoCo a b c By drawing an altitude h we can calculate the area of the triangle. h Area = ½ x base x height What does the sine of A o equal ? Change the subject to h. h = bsinA o Substitute into the area formula.

3. Using The Formula. Example 1 Find the area of the triangle below: 39 o 12m 7m Write down the area formula: Identify b,c and A o b = 7c = 12A o = 39 o Substitute the values into the formula. Calculate the area. A = 42 x 0.629 A = 26.4cm 2

4. Example 2 Find the area of the triangle below: 123 o 19m 13m Write down the area formula: Identify b,c and A o b = 13c = 19A o = 123 o Substitute the values into the formula. Calculate the area. A = 123.5 x 0.839 A = 103.6 cm 2

5. What Goes In The Box ? Calculate the areas of the triangles below: (1) 23 o 15cm 12.6cm (2) 71 o 5.7m 6.2m (3) 151 o 17mm 9mm A =36.9cm 2 A =16.7m 2 A =37.1mm 2