use an inverse trig function to write è as a function of x

Question

(There is a right triangle.
The hypotenuse is 2.
è is the angle between the base and the hypotenuse.
The base/adjacent side of è is (x + 1)
The side opposite è does not have a value.)

a) è = sqrt [4 - (x + 1)^2] all divided by 2

b)è = cos ^ -1 [(x + 1)/2]

c)è = tan ^ -1 [(x + 1)/2]

d)è = sin ^ -1 [2/(x + 1)]

How do I do this? I'm leaning towards B, the inverse cosine because only the adjacent side and hypotenuse are given. The opposite side is not given, and there is already a variable x in the given adjacent side.