Definition:Cartesian Plane/Quadrants
Definition
For ease of reference, the cartesian plane is often divided into four quadrants by the axes:
First Quadrant
Quadrant $\text{I}: \quad$ The area above the $x$-axis and to the right of the $y$-axis is called the first quadrant.
That is, the first quadrant is where both the $x$ coordinate and the $y$ coordinate of a point are positive.
Second Quadrant
Quadrant $\text{II}: \quad$ The area above the $x$-axis and to the left of the $y$-axis is called the second quadrant.
That is, the second quadrant is where the $x$ coordinate of a point is negative and the $y$ coordinate of a point is positive.
Third Quadrant
Quadrant $\text{III}: \quad$ The area below the $x$-axis and to the left of the $y$-axis is called the third quadrant.
That is, the third quadrant is where both the $x$ coordinate and the $y$ coordinate of a point are negative.
Fourth Quadrant
Quadrant $\text{IV}: \quad$ The area below the $x$-axis and to the right of the $y$-axis is called the fourth quadrant.
That is, the fourth quadrant is where the $x$ coordinate of a point is positive and the $y$ coordinate of a point is negative.
Note that the axes themselves are generally not considered to belong to any quadrant.
Sources
- 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 5$: Trigonometric Functions
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): Cartesian coordinate system
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): quadrant
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): Cartesian coordinate system
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): quadrant