Answer:
your choices are correct
Step-by-step explanation:
sin(x +π/2) is a translation of the sine function to the left by π/2 units, which makes it look exactly like the cosine function that you want.
cos(-x) is the same as cos(x), since the cosine function is an even function.
___
sin(x -π/2) will look like -cos(x), not what you want.
The third choice is a reflection across the x-axis of the function you started with. It is not equivalent.
