What is the frequency of #f(theta)= sin 3 t - cos 15 t #?

1 Answer

Period is #(2pi)/3# and the frequency is its reciprocal, #3/(2pi)#.

Explanation:

Period of sin (3t) --> #(2pi)/3#
Period of cos (15t) --># (2pi)/15#
Period of f(t) --> least common multiple of #(2pi)/3# and #(2pi)/15#

#(2pi)/3# ...x (1) --> #(2pi)/3#
#(2pi)/15# ...x (5) --> #(2pi/3)#

Period of f(t) --> #(2pi)/3#.

The frequency = 1/(period)=#3/(2pi)#.