- 9

- 0

**2. Homework Equations**

x = A*cos([tex]\omega[/tex]*t+[tex]\phi[/tex])

**3. The Attempt at a Solution**

At t=0, [tex]\omega[/tex]*t = 0, so x = A*cos([tex]\phi[/tex]). Therefore, [tex]\phi[/tex] = arccos(x/A) = arccos(.8) = 36.87.

The acceleration is negative and the velocity is positive, so the angle is 360 - 36.87 = 323.13 degrees, right?