Vectors Joining Two Points

You might already have come across the term vector. A quantity which has magnitude, as well as direction, is represented by a vector. The most common example of a vector in mathematics is a directed line segment. Let us say that a line AB, 5 cm in length, is pointed towards the south. In this case, AB is a vector.

In Maths, there are different types of vectors. Basic mathematical operations can be applied to them as well. In this article, we will talk about a vector which joins two points.

Equation of Vectors Joining Two Point

We can represent a point by its x coordinate, y coordinate and z coordinate. Let us say there are two points represented by their x-, y- and z- coordinates as:

  • P1(x1,y1,z1)
  • P2(x2,y2,z2)

We join the points P1 and P2 by a vector and call it as P1P2.

Vectors Joining Two Points

We represent the vectors from the origin O along the x-, y- and z-axes as i, j and k respectively. Now we join the origin O to P1 with the vector OPand to P2 with the vector OP2. Using the triangle law, we get:

OP1+P1P2=OP2

Or

P1P2=OP2OP1

That is,

P1P2=(x2i^+y2j^+z2k^)(x1i^+y1j^+z1k^)

=(x2x1)i^+(y2y1)j^+(z2z1)k^

Thus, the above equation represents the vector P1P2. Its magnitude can be given by:

P1P2=(x2x1)2+(y2y1)2+(z2z1)2

Solved Examples

Question 1: Find the vector and its magnitude which joins the point A with coordinates (4, 5, 6) to point B with coordinates (10, 11, 12).

Solution: The vector is directed from the point A to B and can be denoted by 

AB

Thus,

AB=(104)i^+(115)j^+(126)k^=6i^+6j^+6k^

Magnitude can be given by:

AB=62+62+62=36+36+36=108=10.39

Question 2: Find the vector joining the points P(1, 2, 3) and Q(6, 5, 4) directed to Q from P.

Solution:

The vector which is directed from the point P to Q can be written as

PQ

Therefore,

PQ=(61)i^+(52)j^+(43)k^=5i^+3j^+k^

To learn more about vectors, section formula and other vector concepts with illustrative examples, by watching interactive video lectures on them, download BYJU’S – The Learning App.

Quiz on Vectors joining two points

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  1. Helpful thanks for sharing this .