Question

Which of the following functions is periodic?
f(x)=x^3+5
f(x)=2x+5
f(x)=cosx+5
f(x)=2(sq.rt.)x+5

Answer 1

f(x) = Cos x + 5

Answer 2

f(x)=cosx+5. All trigonometric functions are periodic. Because of this property trig functions can be used to model a lot of natural phenomena that are periodic for example, the tides, oceans waves, light waves etc.