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What Are You Plotting?

Investigate the positions of points which have particular x and y coordinates. What do you notice?

Dotty Relationship

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2
On the grid below, join the two blue dots, A and B, together with a straight line.

Now join the green dots, C and D, with a straight line.

grid with four dots marked
At what angle do the two lines cross?

Investigate the number of squares "along" and "down" from A to B compared with the number of squares "along" and "up" from C to D. What do you notice?

Using what you have found out, can you draw lines that are perpendicular (at $90^{\circ}$) to the lines drawn below?

line connecting points by 3 along and 3 up
line connecting points by 4 along 1 down
line connecting points by 1 along 3 down
Is there only one solution each time?

Do the two lines have to be the same length? Why or why not?