# Coordinate Geometry Formulas, Solutions, Study Material

## Coordinate Geometry important questions on Page No - 6

We studied about coordinate axes, coordinate plane, plotting of points in a plane, distance between two points, section formula, etc. All these concepts are the basics of coordinate geometry. Let us have a brief recall of coordinate geometry done in earlier classes. To recapitulate, the location of the points (6, – 4) and (3, 0) in the X-plane is shown in * (Fig 10.1)*.

We may note that the point (6, – 4) is at 6 units distance from the y -axis measured along the positive x -axis and at 4 units distance from the X –axis measured along the negative Y-axis. Similarly, the point (3, 0) is at 3 units distance from the Y –axis measured along the positive X -axis and has zero distance from the X -axis. We also studied.

**1. ** Distance between the points

**2.** The coordinates of a point dividing the line segment joining the pointsinternally, in the ratio m: n are

**Example: **he coordinates of the point which divides the line segment joining A (1, –3) and B (–3, 9) internally, in the ratio 1: 3 are given by and

**3. ** In particular, if m=n ,the coordinate of the mid point of the line segment joining the point . Are

**4. ** Area of the triangle whose vertices are

Note : If the area of the triangle ABC is zero , then three point A,B and C lie on a line , i.e ,they are collinear .

We shall continue the study of coordinate geometry to study properties of the simplest geometry figure –straight line. Despite its simplicity , the line is a virtual concept of geometry. and enters into our daily experience in numerous interesting and useful ways. Main focus is on representing ,the slope is most essential.

**Slope of a Line:** A line in a coordinate plane forms two angles with the x-axis ,which are supplementary The angle (say)

Θ made by the line l with positive direction of x -axis and measured anti clockwise is called the inclination of the line. Obviously 0° ≤ θ ≤ 180° * (Fig 10.2) *.

We observe that lines parallel to x -axis, or coinciding with x -axis, have inclination of 0°. The inclination of a vertical line (parallel to or coinciding with y -axis) is 90°

**Definition:** If θ is the inclination of a line l , then tan θ is called the slope or gradient of the line l . The slope of a line those inclination is 90° is not defined. The slope of a line is denoted by m . Thus, m = tan θ, θ ≠ 90° It may be observed that the slope of x -axis is zero and slope of y -axis is not defined.