Oscillation problems

Sup' /sci/ !

We have somme problems with an exercise. We have the harmonic equation [tex] x(t) = -0,086 \sin \left( 5t - 0,927 \right) [\tex]
and we're asked to find out the first time (so over 0 second) where the [tex]v_x[\tex] (in [tex] V(v_x, v_y)[\tex] is positive and equal to 60 percents of its maximal value.

Please /sci/, I need your help !

so
0.6 = -0.086 sin (5t - 0.927)
0.6 / (-0.086) = sin (5t - 0.927
(arcsin (0.6/-0.086) + 0.927)/5 = t, which is your answer

actually, no
its max value is 0.086, so its slightly different, my bad
you can just do 0.6 = sin (5t - 0.927)

Okay thanks a lot, that really helped me.