2D Coordinates
What are 2D coordinates?
- A graph in two dimensions is also known as a Cartesian plane
- The two dimensions are usually labelled x and y
- The horizontal axis is x and the vertical axis is y
- The two axes meet where x and y are both 0
- This point, (0, 0), is known as the origin
- The coordinate (x, y) tells you the position of the point relative to the origin
- For the x value
- A negative value means that the point is x units to the left of the origin
- A positive value means that the point is x units to the right of the origin
- For the y value
- A negative value means that the point is y units below the origin
- A positive value means that the point is y units above the origin
- For the x value
Examiner Tip
- "Along the corridor, up the stairs" is a useful way of remembering which way round (x, y) is.
- Pay close attention to the scale shown on the axes.
Worked example
(a)
Write down the coordinates of the point A shown on the axes below.
(b)
Mark the point B (3, -2) on the axes below.
(a)
A is 3 left of the origin so x = −3
A is 4 above the origin so y = 4
(−3, 4)
(b)
Starting at the origin, count 3 squares right and two squares down
Mark the point with a solid circle or a cross
