This article describes how to plot points in a two dimensional plane and measure Euclidean distance between two points.

The plane that we write in a paper or draw something is a two dimensional plane because it has length and width. On the other hand, the plane that we live in a house is a three dimensional plane because it has length, width and height. Here we will discuss two dimensional plane and plots. Two dimensional plane is conventionally denoted as x-y plane where x is the horizontal axis and y is the vertical axis. The intersecting point of x-axis and y-axis is called the origin C (0, 0) meaning that at this point x-value is zero and y-value is also zero.

From origin if we move right side in x-axis the value of x is positive and in the left side its value is negative. Similarly, from the origin if we move up in y-axis, the value of y is positive and in the downside the value of y is negative. Any point in (x, y) plane is denoted as (x value, y value).

Let us locate a point  P (3, 7) in the following figure. Negative x-axis and negative y-axis is represented as x^’ and y^’.  This graph paper contains small box which is the unit cell and we can define the unit cell as we wish. For example, we can define each unit cell is equal to 1 or 2 or 3 and so on. So, if we define each unit cell as 1 unit, we need to move in positive x direction 3 units and then move upward 7 units. Similarly, we can locate point Q (-3, -7) by moving negative x direction 3 units and then downward direction 7 units as shown in the figure.

If we define each unit cell as 0.5 units or two unit cells equal to 1, then we just need to move double the x-value and y-value units to get the desired values. The distance between two points for example      p₁(x₁, y₁) and  p₂(x₂, y₂)  can be found using the following equation,

d(p_1, p_2) = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\