Finding functions for sin and cosine graphs?

I really need help on answering these, even helping with one would benefit me a lot.
Here are pictures of the problem I'm trying to solve:
1. Graph: http://gyazo.com/ff6f951027f4c622c7caf58...
Question: http://gyazo.com/d0e0896adc4ee22f8e37ae4...

2. Graph: http://gyazo.com/609da9c4e7d26075f2cc234...
Question: http://gyazo.com/0f1714ab35970d474d0ae1e...

3. http://gyazo.com/fba72f5112fa2df26d643c4...
Question: http://gyazo.com/59894de5b75cf9e70a7d4d7...

Oh and for this one, All i need help is with finding the phase shift
Graph: http://gyazo.com/cf85b1ec4ab5107611f17e9...

y = a sin b(x±h) ± k
a : amplitude => take absolute value
b : angular frequency
h : horizontal shift ( phase shift). (+ left, - right)
k : mid. line or vertical shift ( + up, - down)
period = 2π/b ( for sines, cosines. if tangent : p = π/b)
.........................................
1.
f(x) = -4sin[(π/2)x]
http://www.wolframalpha.com/input/?i=plo...
2.
f(x) = -4sin[(π/2)x] + 3
http://www.wolframalpha.com/input/?i=plo...
3.
f(x) = -cos[π/5(x-1)]
http://www.wolframalpha.com/input/?i=plo...

4.
f(x) = 0.5sin[π(x-0.2)]
http://www.wolframalpha.com/input/?i=plo...