Answer:
y = sine (x + 90 degrees)
Explanation:
y = cosine(x) is a curve that crosses the y-axis at y = 1 and completes one cycle at 360 degrees.
sine(x) have the same curve than cosine(x), but translated 90° to the right respect cosine(x)
f(x + c) translates f(x) horizontally c units to the left.
Then, sine(x + 90) is equivalent to cosine(x)