# Homework Help: Graphing pendulum function

1. Jan 23, 2005

### No Name Required

Hello,

Ive done the first part of a question which was to derive the equation

$$\displaystyle{\theta(t) = \theta_0 \sin(\omega_0t + \phi)}$$

for a pendulum

where $$\displaystyle{\omega_0 = \sqrt{\frac{g}{r}}}$$ and $$\displaystyle{\phi = \sin^{-1} \left(\frac{\theta_1}{\theta_0}\right)}$$

$$r = \mbox{length of rod (pendulum)}$$

The next part says

Sketch $$\theta(t)$$ versus $$t$$ for the cases $$\phi = 0$$ and $$\displastyle{\phi = \frac{\pi}{2}}$$

How do I do this if i dont know $$\theta_0$$ or $$r$$? I know they are both constant though, does this have a bearing on the situation?

Thankyou

Last edited: Jan 23, 2005
2. Jan 23, 2005

### dextercioby

1.There's a typo in the first formula.A "t" is missing in the (round) bracket...

2.The graph is basically a streched (on "y") sinusoid...So it ain't a big deal to draw it.You have to determine the amplitude,the zeros and that's it...

Daniel.

3. Jan 23, 2005

### No Name Required

thankyou...

Ok, so im just basically sketching it and trying to make it look nice

I think i can do that

Thanks again