# Help with trigonmetric function question

1. Jun 4, 2004

### maccaman

This is a problem solving one, i just dont know where to start it though

The speed of a particle in an alternating current is given by the equation:

v = 3 cos t/3, where v is in cm/s and t is in seconds.

The particle's movement begins at its point of equilibrium.
How soon after the start would the particle first reach a displacement of
-4.5cm?

2. Jun 4, 2004

### Integral

Staff Emeritus
You are given an expression for the velocity, you need to find the displacement.

$$v = \frac {dx} {dt}$$

so

$$\frac {dx} {dt} = 3 cos (\frac t 3)$$

$$\int dx = \int 3 cos (\frac t 3) dt$$

You should now be able to find an expression for the displacement as a function of time. You will need to find the time that satifies your conditions.

Last edited: Jun 4, 2004