Plotting solutions to first order system The question gives the initial value problem $\dfrac {\Bbb d^2y} {\Bbb dt^2} + y = 0$ with the initial conditions $y(0) = 0, y'(0) = v(0)=1$, and that $y(t) = \sin t$ is a solution.

The question asks to plot the solution curve to the solution. Do I just draw the $\sin$ curve? Is it asking for a closed system shape?
Draw the three curves approximately as function of time $t$.

$ Sin, Cos, -Sin $ 

The question wants you to recognize that graphs 1 and 3 are same except sign!
Draw the three curves approximately as function of time $t$.

$ Sin, Cos, -Sin $ 

The question wants you to recognize that graphs 1 and 3 are same except sign!