How to use this applet:
To Play The Game:
When the "aim is" button is pressed, an alien and a viewfinder appear on the screen. The position of your aim (the viewfinder) is given by the computer. The position of the alien is always at the relitive perpendicular vector of the aim. The purpose of the game is that you input your guess at where the alien is positioned. If you hit him your score goes up and, ultimately you learn to get the relitive perpendicular to a vector. There is a hint button if you really need it.
Notes on the maths used in the applet:
If we have a vector r=ai+bj, then the relative perpendicular vector, n,to that vector is given by rotating the given vector r, anticlockwise, through a 90 degree angle.
The quick way to do this is, take the vector r=ai+bj and swop its coefficients, a and b around, changing the sign of the second coefficient.
Example: The perpendicular vector of, r=ai+bj, is n=-bi+aj.
NOTE: |r| = |n|.
