I need to find the laplace transforms of these functions:

a) (t-1)^4 <---dont know which property to use

b) t*exp(-t)*sin(2t)

c) cos(kt)^2 k = constant

Any help would be great.

My attempts are:

b) 1/s^2 * F(s+1)*4/(s^2+4)

Answer should be: 4(s+1)/[(s+1)^2+4]^2

c) Answer should be: 4(3s^2-4)/(s^2+4)^3