# Sin/cos/tan of theta

1. Dec 2, 2003

### BluE

Hello, I'm studying pendulums and their proporties, and I really need to know the sin/tan/cos of theta. If anyone can help, please help. (And also, I need to know what theta is)

And if you don't understand what I'm asking, please ask and I'll try to explain to the best of my ability.

--Thank you

2. Dec 2, 2003

### chroot

Staff Emeritus
$\theta$ is a symbol commonly used to denote an angle. What angle? I don't know, you'd have to tell me, since you're the one looking at the problem. Most likely, for a pendulum problem, $\theta$ means the angle between the pendulum's string and a vertical line. This angle is constantly changing as the pendulum swings back and forth.

The sine, cosine, and tangent are functions. They're like little machines: you give them an angle, and they give you back a number. For example, the cosine of zero degrees is one: if you insert "zero degrees" into the "cosine machine," it spits out the number "one."

Maybe you should post the entire problem for us here so we can better help you.

- Warren

3. Dec 2, 2003

### BluE

Actually, there is no problem, I just don't know what is being talked about. (I really don't know if I even explained it right to you)

http://www.gyogyitokezek.hu/fe/pendtutor1.htm [Broken]

This is a sight, and the one I'm looking at is the "plane pendulum."

Last edited by a moderator: May 1, 2017
4. Dec 2, 2003

### chroot

Staff Emeritus
Then you're not talking about theta, you're talking about phi ($\phi$). The meaning of this symbol is shown in Fig. 2 on the site. It is the angle of the pendulum, measured anticlockwise with respect to some point on the circle (shown there on the bottom of the circle).

- Warren

5. Dec 2, 2003

### BluE

Okay, thanks. But I have another question. If I were to make a pendulum to exert force on an object, how do I calculate how much force the pendulum has and how could I control it?

Do I use this equation?:

$$F_{cp}=m\omega^2+mg\cos\phi$$

6. Dec 2, 2003

### PrudensOptimus

Depends on the situation buddy.

7. Dec 2, 2003

### BluE

Okay, say I have a plane pendulum and I want to use it to make contact with a stationary object, thereby causing motion to the object. How do I calculate how much force the pendulum exerts and how can I control it? Say, I know "x" amount of force is needed to move an object from point A to point B. How can I use the pendulum to control and calculate "x" amount of force to give motion to the object?

8. Dec 2, 2003

### chroot

Staff Emeritus
9. Dec 3, 2003

### BluE

Okay, thank you for your time and help.