5.(ii)   The Class X students of a secondary school in Krishinagar have been allotted a rectangular plot of land for their gardening activity. Sapling of Gulmoha  are planted on the boundary at a distance of 1m from each other. There is a triangular grassy lawn in the plot as shown in the Fig. 7.14. The students are to sow seeds of flowering plants on the remaining area of the plot. (ii) What will be the coordinates of the vertices of D PQR if C is the origin?Also  calculate the areas of the triangles in these cases. What do you observe?

           pizza figure

Answers (1)

Taking C as origin, then CB will be x-axis and CD be y-axis.

The coordinates fo the vertices P,Q, and R are: (12,2),\ (13,6),\ (10,3). respectively.

The area of the triangle, in this case, will be:

Area =\frac{1}{2}\left [ x_{1}(y_{2}-y_{3})+x_{2}(y_{3}-y_{1})+x_{3}(y_{1}-y_{2}) \right ]

=\frac{1}{2}\left [ 12(6-3)+13(3-2)+10(2-6) \right ]

=\frac{1}{2}\left [ 36-13+40 \right ] = \frac{9}{2}\ Square\ units.

It can be observed that in both cases the area is the same so, it means that the area of any figure does not depend on the reference which you have taken.