CS100M Spring 2004
A2 FAQ
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Q) I'm getting a weird error in the velocity/height/acceleration problem.
A) You might be multiplying t^2 wrong. There's a bit about matrices
   we haven't covered:

   If t = [1 2 3], then
                                  [1] [1]
   t*t means you are trying to do [2] [2], which is NOT a true dot product.
                                  [3] [3]

   You would need to say tt'. But, you don't even want a dot product in the
   first place. Instead, do t.*t (yes, ".*) for array multiplication, which
   multiplies each element of t by itself.


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Q) When I try cos(pi/2) in MATLAB, it is not equal to zero.

A) This is because of rounding errors in MATLAB.  Write your code for the 
   problem in question as if there were no rounding errors.  I found that
   tan(90) did not produce an exceptional case, whereas tan(270) did. **In fact
   I had previously made a mistake.  tan(270) does not execute the error branch
   either.  Write the code so that it would print out the error if there was a 
   case we could check.  In other words, make sure you have an if statement for
   the error case.

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Q) So wait, on the tangent question, does that mean I need to implement the if
   statement for the error case even if it doesn't get executed?

A) Yes, implement the if statement for the error case for the tangent problem,
   even though it will not get executed for tan(90) for example.

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