Answer to Quiz 10 Fri 11 Nov 2005

Consider the linear system
```
   {  2 x1 + 3 x2 = 1
   { -2 x1 +   x2 = 3.
```
Give all the MATLAB commands to define this linear system in the format A x = b, with x = [x1 x2]^T, i.e.: what are the commands to define A and b?
What is the solution of this system? Give all relevant MATLAB commands.
Answer:
```
       A = [2  3; -2  1]
       b = [1; 3]
       x = A\b
     
       x =
            -1
             1
```
Consider the curve in polar coordinates defined by r(t) = t sin(t).
Give all MATLAB commands to make the plot for t in [-1,+1]. Sketch the curve.
Answer:
```
       t = -1:0.01:1;
       r = t.*sin(t);
       polar(t,r)
```