Move the blue points in the applet below to create a square.[br]When you think you've made a square, you can check to see if you're correct.[br]Use the 'Reset' button to randomly place the two black points in new positions.[br]

Do you have a strategy for working out where to place the two blue points?[br][br]Is it always possible to make a square?[br][br]If the two black points had coordinates (a,b) and (c,d), can you find a way to write the coordinates of the two blue points in terms of a, b, c and d?