This topic falls under “Coordinate Geometry“. We will learn the following topics today.
The Distance Formula (refer to the diagram as well)
Let the two given points be and
In the diagram, you can see that the is a right angled triangle and
. Which means that
(Pythagoras Theorem)
Given and
Hence
Therefore the distance between any two points and
is
Notes: If a point is on , its ordinate is
, therefore the point on
is taken as
. Similarly, if the point is on
, its abscissa is
, therefore the point on
is taken as
.
Three points are said to be co-linear if and only if (as shown in the diagram). Which means that the distance from
plus the distance from
is equal to the distance from
.
Circumcentre of a Triangle
It is a point that is equidistant from the three vertices of a triangle. i.e. if point
is equidistant from the three vertices
, then
of
.
What this means is that if a circle is drawn with as the center and any of the vertices as the radius, the circle will touch all the three vertices of the
.
Section Formula
This is used to find a point that divides a line segment joining two points in a given ratio.
Let be the line segment. Let coordinates of
and
.
Let be a point dividing
in the ratio of
.
We need to find .
Refer to the diagram.
Since and
are similar
Note: If instead of you used
, then the formula would become as follows:
Points of Trisection
Let points lie on a line segment
such that it divides the line in three equal parts i.e.
Point divides the line segment
in the ratio of
Similarly, point divides the line segment
in the ratio
Midpoint Formula
Let points lie on a line segment
such that it divides the line in two equal parts i.e.
Point divides the line segment
in the ratio of
The centroid of a Triangle
The centroid of a triangle is the point of intersection of its medians and the centroid divides each of the medians in the ratio of .
To find the coordinates of the centroid:
- First, find the coordinates of the midpoint of the sides of the triangle.
- The find out the coordinates of the centroid
between the vertex and the opposite midpoint.