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SAI International School
                                                       CLASS - X

               Mathematics
               CHAPTER-7: Co-Ordinate Geom-3Lesson Notes-3




               SUBTOPIC : Area Of Triangle


               Area of a Triangle



























               Here ABC is a triangle with vertices A(x 1, y 1), B(x 2, y 2) and C(x 3, y 3). To find the area of the triangle we need to draw
               AP, BQ and CR perpendiculars from A, B and C, respectively, to the x-axis. Now we can see that ABQP, APRC and
               BQRC are all trapeziums.
               Area of triangle ABC = Area of trapezium ABQP + Area of trapezium APRC – Area of trapezium BQRC.





               Therefore,







               Remark: If the area of the triangle is zero then the given three points must be collinear.

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