# Extra Questions Class 9 Maths | Coordinate Geometry Q3

###### NCERT Chapter 3 | Area of Right Angled Triangle | Cartesian Plane Class 9 Maths Questions

Question 3: What is the area of the triangle formed by joining the lines (8, 0), (12, 0), and (12, 4)?

## NCERT Solution to Class 9 Maths

### Explanatory Answer | Chapter 3 Extra Question 3

The coordinates of the vertices of the triangle are marked in the x-y plane and the triangle has been constructed by joining these vertices as shown in the figure given below.

Let the coordinates of the vertices A, B, and C be (8, 0), (12, 0), and (12, 4) respectively.
The ordinate (y-coordinate) of points A(8, 0) and B(12, 0) are 0. So, both these points lie on the x – axis.
The line joining (12, 0) and (12, 4) is a line parallel to y – axis because the abscissa (x-coordinate) of both points are the same.

Length of AB = 4 units
Length of BC = 4 units

ABC is a right triangle because its base lies on x-axis and side BC is a line parallel to y-axis.
Its base measures 4 units and its altitude measures 4 units.

Therefore its area = $\frac{1}{2}$ x 4 x 4 = 8 sq units

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