Total energy oscillation problem

[vande060]

Homework Statement

The displacement of a mass m = 0.01 kg is x(t) = 0.25m sin(62.83t/s − 0.785398) Find its amplitude, its total
energy, and its speed at t = 0.

Homework Equations

E = Av^2 + Bx^2
x = Asin(wt-theta)

The Attempt at a Solution

i use that above formula to find that Amplitude = .25
speed at t = 0 should be the derivative of the x function i think

v(t) = (.25m)(62.83)cos(62.83t/s - 0.785398)
v(0) = (.25m)(62.83)cos(- 0.785398)

I am not sure about the last part there with finding the energy, any suggestions?

 

[rock.freak667]

Total energy = KE + PE

Total energy = (1/2)kA²