Coordinate Plane

Ways to use it in class

• Across, then up. Call out ordered pairs and have students plot them, saying "across" for x and "up" or "down" for y.
• Quadrant signs. Plot one point in each quadrant and compare the signs of their coordinates.
• Shapes and area. Plot the corners of a rectangle or triangle, close the shape, and check the area by counting squares.
• Reflections. Plot (4, 3), then (−4, 3) and (4, −3): flipping across an axis changes one sign.
• Mystery picture. Read out a list of points to join in order and see what appears.

Questions teachers ask

What is a coordinate plane?

A flat grid made by two number lines that cross at zero: the x-axis across and the y-axis up and down. Every point on it has an address, an ordered pair (x, y), that says how far to go across and then how far up or down.

How do you plot a point like (3, −2)?

Start at the origin, where the axes cross. Move 3 across to the right, because x is positive, then 2 down, because y is negative. Type (3, -2) above and press Plot to check.

What are the four quadrants?

The four regions the axes cut the plane into, numbered counterclockwise from the top right. In quadrant I both coordinates are positive, in II x is negative, in III both are negative, and in IV y is negative.

How do I find the area of a shape on the coordinate plane?

Plot its corners in order, tick Join points and Close shape, and the tool gives the area in square units. Students can check it by counting squares or by splitting the shape into rectangles and triangles.

Can I print coordinate graph paper?

Yes. Choose four quadrants or the first quadrant and the size, press Clear for a blank grid, and press Print.