1. Chapter 7 Coordinate Geometry 7.1 Midpoint of the Line Joining Two Points 7.2 Areas of Triangles and Quadrilaterals 7.3 Parallel and Non-Parallel Lines 7.4 Perpendicular Lines

2. 7.2 Areas of Triangles and Quadrilaterals In this lesson, you will learn how to find the areas of rectilinear figures given their vertices. Coordinate Geometry Objectives

3. ABC is a triangle. We will find its area. Construct points D and E so that ADEC is a trapezium. Coordinate Geometry Area of Triangles

4. ABC is a triangle. The vertices are arranged in an anticlockwise direction. We will find its area. Construct points D, E and F on the x-axis as shown. Coordinate Geometry

5. From the previous slide, we know that Definition Coordinate Geometry

6. Find the area of a triangle with vertices A(–2, –1), B(2, –3) and C(4, 3). The vertices A, B and C follow an anticlockwise direction. Coordinate Geometry Example 5

7. Find the area of a quadrilateral with vertices A(x 1, y 1 ), B(x 2, y 2 ), C(x 3, y 3 ) and D(x 4, y 4 ), following an anticlockwise direction. Split the quadrilateral into two triangles. Coordinate Geometry Area of Quadrilaterals

8. The area of a quadrilateral with vertices A(x 1, y 1 ), B(x 2, y 2 ), C(x 3, y 3 ) and D(x 4, y 4 ), following an anticlockwise direction. The method for finding the area of quadrilaterals is very similar to that of triangles. Coordinate Geometry

9. Find the area of a quadrilateral with vertices P(1, 4 ), Q(–4, 3), R(1, –2) and S(4, 0), following an anticlockwise direction. Coordinate Geometry Exercise 7.2, qn 2(b)