# Point to coordinate function

I am working on a game in which I need an enemy ship to point towards the player.

Here is the equation I came up with:

angle = sin-1(abs(y1 - y2)/√(x1 - x2)2-(y1 - y2)2)

This essentially takes the inverse sine of the opposite divided by the hypotenuse. Unfortunately, this algorithm does not work. Any ideas as to what I need to change? Note, the angle is a radian value.