What is the frequency of #f(theta)= sin 18 t - cos 81 t #?

1 Answer
Feb 22, 2017

The frequency is #=9/(2pi)#

Explanation:

The period of the sum of 2 periodic functions is the LCM ot their periods

The period of #sin18t# is #=2/18pi=1/9pi=9/81pi#

The period of #sin81t# is #=2/81pi#

The LCM of #9/81pi# and #2/81pi# is #=18/81pi=2/9pi#

The period is #T=2/9pi#

The frequency is #f=1/T=9/(2pi)#