Conjecturing sinusoids using a CAS?

I really have no idea what any of this means, and I think I just need a translation...

Let $\displaystyle y=sin(ax) + cos(ax)$.

Use the symbolic manipulator of a computer algebra system (CAS) to conjecture the following:

a) Express y as a sinusoid for a=2,3,4 and 5

b) Conjecture another formula for y for a equal to any positive integer n.

c) Check your conjecture with a CAS.

d) Use the formula for the sine of the sum of two angles to confirm your conjecture.

Now, I have no idea what a symbolic manipulator, computer algebra system, or sinusoid is. I have a TI-84 and I really have no idea what just happened... help?