# Help with some Math (Probably easy)

#### dudeim

##### New Member
Hey,

as I'm not that much of a math genius, well not much of a math anything I need some help with a calculation.

What I want to do is I'm gonna fire an arrow towards an angle that the player can just click.
So the player clicks to his precise left (for example) the arrow flies that way and then I want to know when the arrow is like 800 range further or 1000 range further etc.. so i can destroy it.

Can anyone help me with this?
I know I didn't explain it too good if you need extra description just ask

Thanks!

Well, you can always attach the starting XY coordinates to the projectile. Then when you move that projectile, check the distance between its current and starting positions:

JASS:
``````
function DistanceBetweenXY takes real x1, real y1, real x2, real y2 returns real
return SquareRoot((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1))
endfunction

private method periodic takes nothing returns nothing
local real x=&lt;New X&gt;
local real y=&lt;New Y&gt;
call SetUnitPosition(this.dummy,x,y)
if DistanceBetweenXY (x,y,this.strX,this.strY)&lt;=800. then
call this.stopPeriodic()
endif
endmethod``````

That is pretty smart gonna try it! thanks

Better idea is to increase the distance moved on every interval, and compare that to the maximum range.

Well as I'm not calculating the distance itself every interval (using a system for it) I think it's easier to go with luorax's way.

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