finding the angle of a triangle using tan

Question

alright so im making a ai for a zombie in one of my games, but when i try to rotate the zombie so that he is facing the player everything goes out of wack. they rotate the wrong way, spin around when i get close even though the angle shouldn't change. here is some of my code: ps ignore the z, this game is 3d but im only rotating on on axis so i can code this as though it was xy.

//get camera/player yx
float PlayerYPosition = Player.getPosition().y;
float PlayerXPosition = Player.getPosition().z;
//get zombie yx
float ZombieYPosition = Zombie.getPosition().y;
float ZombieXPosition = Zombie.getPosition().z;
//get side lengths
float sideY = (CameraYPosition - ZombieYPosition);
float sideX = (CameraXPosition - ZombieXPosition);
//get angle
float angle = (float)Math.atan2(sideX,sideY);
//move decimal place out so ex: 0.90f is 90.0f
float ans = angle * 100;
//set rotation of zombie
super.setRotY(ans);

Answer 1

Math.atan2 returns its value in radians, not degrees. To convert to degrees, multiply by either 180/pi or 360/(2 pi):

float ans = angle * 180 / Math.PI;

Java even has a builtin function for this, Math.toDegrees: (thanks @yshavit)

float ans = Math.toDegrees(angle);

Also, what @yshavit says in the comments: you should be using radians throughout the code. But that's perhaps too much work, or you might rely on 3rd party libraries which work with degrees.