An object with mass $0\mathrm{.}170kg$ is acted on by an elastic restoring force with

force constant $11\mathrm{.}0\frac{N}{m}.$ The object is set into oscillation with an initial

potential energy of $0\mathrm{.}150J$ and an initial kinetic energy of $6\mathrm{.}50{10}^{-2}J.$

What is the value of the phase angle $$

if the initial velocity is positive and the initial displacement is negative?

Express your answer in radians.