Using Mathematica to solve an ODE

[Ashley1nOnly]

Homework Statement

Homework Equations

The Attempt at a Solution

I used the NDSolve function from mathematic but its giving me problems. What is the correct way to enter the equation?[/B]
soln = NDSolve[{y''[t] = (-9.8/5)*sin (t), y[0] = 20, y, {x, 0, 12}}]

 

[phyzguy]

(1) The right hand side is not sin(t), it is sin(y[t]).

(2) Look more carefully at the syntax of the Mathematica NDSolve example below. Is your input in this form?

s = NDSolve[{y'[x] == y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}]