# Trig. pendulum question

• June 11th 2008, 08:08 PM
cityismine
Trig. pendulum question
The bottom of a pendulum traces an arc 3 feet in length when the pendulum swings through an angle of 1/2 radian. Find the number of feet in the length of the pendulum.
• June 11th 2008, 09:23 PM
TheEmptySet
Quote:

Originally Posted by cityismine
The bottom of a pendulum traces an arc 3 feet in length when the pendulum swings through an angle of 1/2 radian. Find the number of feet in the length of the pendulum.

The sector of a cricle is given by the formula

$S=r \theta$ where theta is in radians so we get

$3ft=r\left( \frac{1}{2}rad\right) \iff r=6ft$

So the length of the pendulum is 6ft.