How do I use dsolve to find the solution to u'' + u = 3cos(wt) , u(0) = 0, u'(0) = 0 ?

I want to say my problem is me having trouble entering the u'' and the constant w, but I am lost in general as I am fairly new to MatLab.

syms u w t 
eqn = diff(diff(u)) + u == 3* cos(w*t)
dsolve(eqn)

Answer 1

[Walter Roberson]

syms u(t) w
du = diff(u);
eqn = diff(du) + u == 3* cos(w*t)
dsolve(eqn, u(0) == 0, du(0) == 0)