A simple harmonic oscillator has a displacement as a function of time given by $x(t)=$Acos$(\frac{2t}{T}).$ When a quarter of the oscillator's energy is potential energy, what is its displacement from equilibrium?

Note that it may not be necessary to use every variable. Use the following table as a reference for each variable:

For Use

$A$ A

$T$ T

$x=+-$