Velocity/displacement problem

Hello,

I am not very good at calculus to begin with, especially word problems and velocity problems. I have no idea how to start this one out, so if someone could show me how, that would be great to give me a start. Here goes:

The displacement (in centimeters) of a particle moving back and forth along a straight line is given by the equation of motion *s* = 5sin(*π**t*) + 2cos(*π**t*), where *t* is measured in seconds. (Round all answers to the nearest hundredth.)

there are multiple sub-questions, but I'll just give two:

(a) Find the average velocity during the time period [1, 2] (in cm/s).

(e) Estimate the instantaneous velocity of the particle when *t* = 1 (in cm/s).

I haven't the slightest clue other than I'm (guessing) it has something to do with Galileo's law, s(t) = 4.9t^2,but I have no clue where/when I should apply it or in addition to another formula.

Any help would be awesome! Thanks. :)