Please don't just give me the answers (I can use my calculator for that), but explain how you get them by hand so I can understand them.

1) limit as Δx approaches zero OF (cos(π+Δx) + 1) / Δx

2) The function s(t) = -4.9t^2 + 200 gives the height in meters of an object that has fallen from a height of 200 meters. The velocity at time t = a seconds is given by: limit as t approaches a OF (s(a) - s(t)) / (a - t). At what velocity will the object impact the ground?

I just can't seem to make the algebra work on these two! Thanks for your help!