(a)

The period  of a simple pendulum is .

Where

 :period in seconds.

: length in feet.

Find length as a function of the period .

Squaring on both sides.

Length as a function of the period is .

(b)

Find length of a pendulum whose period is seconds.

Substitute in .

Length of a pendulum whose period is seconds is feet.

(a) Length as a function of the period is .

(b) Length of a pendulum whose period is seconds is feet.