Final answer:
The given differential equation is linear and the dependent and independent variables are y and t, respectively. The equation contains one nonlinear term involving a product of y and sin 2t.
Step-by-step explanation:
The given differential equation is:
(cos t)d²y/dt² + (sin 2t)y = 0
This equation is a linear differential equation. The dependent variable is y and the independent variable is t. The only nonlinear term in the equation is (sin 2t)y, as it involves a product of y and sin 2t.