2. Aim: How do we find the area of triangle using trigonometry? Do Now: In the diagram, ∆ABC and h is the height 1. Find the area of ∆ABC 2. Find sin C A CB h a bc HW: p.563 # 4,6,10,12,19,20

3. Area of triangle We use K to represent the area of a triangle so not to confuse A with the angle A. This formula can be used to find the area of triangle, if the lengths of two sides and the included angle are known.

4. Application: 1.Given the triangle ABC, with AC = 12, BC = 18 and  C = 94 . Find the area to nearest integer. 2. In the diagram, the parallelogram ABCD, find its exact area. D C A 16 B 10 108

5. A farmer has a triangular field where two sides measure 450 yards and 320 yards. The angle between these two sides measures 80 . The farmer wishes to use an insecticide that costs $4.50 per 100 square yards or any part of 100 yards. What will it cost to use insecticide on this field? $3195

6. A triangle has two sides of 30 meters and 26 meters, and the angle between them is an obtuse angle. If the area of the triangle is 300 square meters, find the measure of the obtuse angle to the nearest degree. 130º

7. Two observers are 600 ft apart on opposite sides of a flagpole. The angles of elevation from the observers to the top of the pole are 19º and 21º. Find the height of the flagpole.