Matrix Multiplication - freemathhelp http://www.freemathhelp.com/matrix-multiplication.html
Matrix Multiplication - purplemath http://www.purplemath.com/modules/mtrxmult.htm
Geometric Mean & Similar Right Triangles http://www.mathwarehouse.com/geometry/similar/triangles/geometric-mean.php
Your textbook listed for homework help http://hotmath.com/help/homework/geometry-library.html
Geometric Constructions - mathsisfun.com http://www.mathsisfun.com/geometry/constructions.html
Geometric Constructions - mathopenref.com http://www.mathopenref.com/tocs/constructionstoc.html
Math.com http://www.math.com/homeworkhelp/Algebra.html
Purplemath.com http://www.purplemath.com/modules/
Coolmath.com http://www.coolmath.com/
Mathwords: Terms and Formulas http://www.mathwords.com/
CLASSSCAPE.ORG http://www.classscape.org/