
0.5  0.0  0.0
0.0  0.5  0.0
0.0  0.0  0.5


2    4    6
0  -12   -8
4    0    4

(0.5)I


2    4    6
0  -12   -8
4    0    4

0.5


2    4    6
0  -12   -8
4    0    4


1    2    3
0   -6   -4
2    0    2

Diagonal Matrix

The diagonal matrix (aI) is sometimes useful in computer graphics. Say for example that what you want to compute is:

a Ax

where a is a scalar and x is a column matrix. Sometimes it is convenient to think of this as:

(aI)Ax

Now every operation is matrix multiplication. This is an advantage since matrix multiplication can be done by graphics hardware.

What is (2I)(0.5I)?