Problems with measuring angle

[dudeperfect]

I have this circle right now:

And player is able to rotate the arrow. And when it stops, I want to measure the angle between arrow's head and that black horizontal line in the middle of the centre.

 

Arrow has these properties:

arrow = game.add.sprite(380, 300, 'arrow');

arrow.anchor.setTo(0.5, 0.5);

game.physics.enable(arrow, Phaser.Physics.ARCADE);

arrow.body.maxAngular = 500;

arrow.body.angularDrag = 50;

 

This is the line in update method:

reachMessage.setText('Angle: ' + game.physics.arcade.angleToXY(arrow, 380, 300));

 

The problem is, that it always shows 0. I guess this is because my arrow's anchor is 0.5, but I must set that cause I want to spin arrow from center. What I want to do is measure angle between arrow's head and XY. I tried to change arrow's anchor to 0.5, 0.1 before measuring angle, but it doesn't work. 

 

How can I achieve that?

Thank you, for your help.

[dudeperfect]

PROBLEM SOLVED

[crouzilles]

PROBLEM SOLVED

Nice of you to share, thanks a lot.

Crouz