Math Help - what is the proof that the corelation coefficent falls between -1 and 1

1. what is the proof that the corelation coefficent falls between -1 and 1[RESOLVED]

Why must the correlation coefficient for a straight line be $-1 \leq r \leq 1$

2. This has nothing to do with lines.
Correlation by the Cauchy-Schwarz inequality is between -1 and 1.
http://www.aiaccess.net/English/Glos...hy_schwarz.htm
http://www.aiaccess.net/English/Glos...oefficient.htm