It's a modification of sine function.
- the first picture.
The values of y are in <-2, 2>. Therefore we have
- the second picture.
The zeros of the function on the graph are 0, 2, 4, 6, ... → 2k, k ∈ Z
We know. The zeros of a sine are 0, π, 2π, 3π, ... → kπ, k ∈ Z
Therefore we have the equation:
divide both sides by 2k
Therefore your answer: