Degrees and the Moon--Parallax problem?

You have an isosceles triangle: Observer 1 - Observer 2 - Moon. You know the distance between the observers is 12,756 km. The distance from the Moon to the mid-point between the two observers is 384,400 km. You therefore have two right-angled triangles with sides 12,756/2 and 384,400, i.e. 6,378 and 384,400. The angle at the apex of each of the right angled triangles is arctan(6378/384400). Double this angle to obtain the angle of displacement of the Moon.