Wrong angle while drawing a partial circle with AS3 - actionscript-3

Question

For a flash game project I am working on I want to create a camera which should be able to detect a player through ray-casting. The camera should be able to have different view angles (eg. 45 degrees or 90 degrees), and according to these view angles the ray-casting should vary. Creating the actual view angles using ray-casting doesn't cause a problem, however, for some reason that is beyond me the angles in which these view angles are positioned are wrong.
This is the code I use:
for (var i:Number = 0; i < this._viewAngle; i++)
{
var pointX:Number = (this._viewRange) * Math.cos(this._viewAngle + (i * Math.PI / 180));
var pointY:Number = (this._viewRange) * Math.sin(this._viewAngle + (i * Math.PI / 180));
this._rayHolder.graphics.lineTo(pointX, pointY);
this._rayHolder.graphics.moveTo(0, 0);
}
And this is the result:
(90 degrees)
(45 degrees)
I hope what I wrote was understandable enough, because I don't know how to explain it more clearlyIf anybody could shed some light on what I am doing wrong here, that would be awesome.
EDIT:
Changing Math.cos(this._viewAngle + (i * Math.PI / 180)); to Math.cos((this._viewAngle + i) * Math.PI / 180); results in this:
(90 degrees)
(45 degrees)

Answer 1

I think you're close with your update. As Sunil D points out, you presumably just want to align the vision cone so that it's centred at 90˚ from the vertical. In other words, starting from -_viewAngle * 0.5:
for (var i:Number = 0; i < this._viewAngle; i++)
{
var pointX:Number = (this._viewRange) * Math.cos((-this._viewAngle * 0.5 + i) * Math.PI / 180);
var pointY:Number = (this._viewRange) * Math.sin((-this._viewAngle * 0.5 + i) * Math.PI / 180);
this._rayHolder.graphics.lineTo(pointX, pointY);
this._rayHolder.graphics.moveTo(0, 0);
}
Edit: While these equations work for this application, the following reflect Flash's odd coordinate systems more accurately. Specifically, with positive x to the right, positive y downwards:
for (var i:Number = 0; i < this._viewAngle; i++)
{
var pointX:Number = (this._viewRange) * Math.sin((90 - this._viewAngle * 0.5 + i) * Math.PI / 180);
var pointY:Number = (this._viewRange) * -Math.cos((90 - this._viewAngle * 0.5 + i) * Math.PI / 180);
graphics.lineTo(pointX + 100, pointY + 100);
graphics.moveTo(100, 100);
}