What is the equation of the graph below?

Option A y = sin ( x + 90 )

Step-by-step explanation:

The given graph is the graph of cosine which should be in the form of

y = a cos ( bx + c ) + d

here a = amplitude = = = 1

Since period of the wave is 2x or 360°.

we know, period =

                          = 1

Now equation becomes,

y = cos ( x + c ) + d

In this graph there is no horizontal or vertical shift

c = 0 and d = 0

so equation will be  y = cos (x)

as we know              y = cos (x) = sin ( 90 + x )

Therefore, Option A y = sin ( x + 90 ) is the answer.

a. is correct