1. ## Arc Length

Just a quick question.

Is the arc length $L$ of a circle with radius $r$, made by the angle $\theta$, $L = r \theta$ or $L = 2r \theta$?

Measuring $\theta$ in radians obviously.

Thanks

2. Originally Posted by craig
Just a quick question.

Is the arc length $L$ of a circle with radius $r$, made by the angle $\theta$, $L = r \theta$ or $L = 2r \theta$?

Measuring $\theta$ in radians obviously.

Thanks
When the radius vector completes one rotaτion, it covers an angle 2π radians. The tip of the vector moves through a distance 2πr.
So when the distance moved by tip is L, what the angle covered by the vector?

3. Originally Posted by craig
Just a quick question.

Is the arc length $L$ of a circle with radius $r$, made by the angle $\theta$, $L = r \theta$ or $L = 2r \theta$?

Measuring $\theta$ in radians obviously.

Thanks
Which one gives the correct circumference ( $\theta = 2 \pi$) ....?

4. Thanks for the replies, not sure what happened then, just couldn't visualise it at all

Arc length $L = r \theta$

Cheers for that