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The coordinates of a point give us directions so that we can locate it on a coordinate plane. In this lesson you will learn to describe points in the plane and study the different parts of the coordinate plane.
A point has coordinates $(x, y)$, where $x$ is given by the labels below the coordinate grid, and $y$ is given by the labels to the left of the coordinate grid.
Sometimes we want to name several variables in a way that shows they are related. When we do, we’ll write a variable with a subscripted number. For example, $x_1$ (pronounced “$x$-1” or “$x$-sub-1”) is a variable which is related to (but different from) the variable $x$.
Use the slider to the left to change the value of $x_1$ for the point $(x_1,2)$. Notice how the point moves.
Use the slider to change the value of $y_1$ and notice how the point $(2,y_1)$ moves.
Use the $x_1$ slider to change the $x$-coordinate of the point $(x_1,y_1)$. Use the $y_1$ slider to change the $y$-coordinate of the point. Notice how the point moves. The coordinates of the point are shown below the grid.