How to tell if a function is periodic - an example

Is the function cos(2x) + cos(3x) periodic, and if so, what is the period? In this worked example you'll learn an easy way to approach problems involving periodic functions.

More practice problems with solutions:

[no_name_]

Thank you very much for the clear explaination!

[bluerexgaming]

damn, very good and helpful video. It is clear, and keep up your work

[o.om.m]

If a periodic function has a period of 9 and f(5)=-4 and f(8)=5 what is f(2)? Many thanks

[HAIDERALI-vyrn]

\cos x\ +\ \cos\pi x is not a periodic function so it has no period.