# Yo-yoing over the harmonic oscillator

by DiracPool
Tags: harmonic, oscillator, yoyoing
 P: 5 The second derivative of $-cosθ$ is equal to $cosθ$. Because $[-cosθ]' = -sinθ$ and $[-sinθ]' = cosθ$ so $[-cosθ]'' = cosθ$. Maybe this is also helpfull: http://www.wolframalpha.com/input/?i=x%27%27+%3D+-x
 P: 950 It is not so difficult to use a better notation! Try to see whether x = acos(bt), where a and b are constants, fits with the equation $\frac{d^{2}x}{dt^{2}}$ = -(positive constant)x.