Angle of a line...

[Homer_simpson]

how do i calculate angle A knowing that line1 is always horizontal and having the coordinates of line2...
i know it has to be done using Sine and Cosine but i dont exactly know how....


Haven't had math in while so i've forgotten a few stuff... =/

[Catalyst]

SOH CAH TOA

sin=op/hyp

your hyp is the distance from point1 to point2
since line 2 is always horizontal that distance is y2-y1

angle=sin-1((y2-y1)/distance (p1,p2))

[Andy]

since tan of an angle is the oposite side over the adjancent side, you simply set up an equation of tan(x)=10/20 tan(x)=1/2 then u juss do tan inverse and you get 45 degrees

[SilverSprite]

yepyep just something to add.. since tan is opposite side over adjacent side.. that means that it is simply the slope of the line meaning that tanA where A is the required angle is equal to the slope of the line.. so A = arctand(slope of line)

[Homer_simpson]

hmmm.... got it!!! thx...
here's another question how do i caculate tangent (a) in Turing?

[Andy]

there is no tangent in turing, but since tan(A)=sin(A)/cos(A) just substitute it

[Homer_simpson]

no it's not i thought of that and i tried it b4 it doesn't work !!! =(
Edit:oh wait nvm i used cos instead of cosd now it works...

code:

function tan (r : real) : real     result (sind (r) / cosd (r)) end tan put tan (1)

how do i do arctan or sine-1? **-1 doesn't work =/

[AsianSensation]

funny thing is, the geniuses who made turing(tom) decided not to put a inverse cos and sin function, said it was irrelevant.

so the best bet for using inverse tan is to make one urself....

[Catalyst]

such an old post (this is also in the help file)

http://www.compsci.ca/bbs/viewtopic.php?t=263&highlight=inverse

[AsianSensation]

*stick foot in mouth

whoa, they had an arctan function? damn.......Im ignorant.......

[Andy]

wow that's really cool... make ur own inverse functions

[SilverSprite]

its math dodge.. you go to massey you should undetrstand those..

[Homer_simpson]

i didn't know they had arctan tangent in turing either... in fact that was all that i needed...
so here's how it goes:

code:

View.Set ("offscreenonly") var x1, x2, y1, y2, b := 0 var slope, ang : real x1 := 100 y1 := 100 loop     mousewhere (x2, y2, b)     drawline (0, y1, 640, y1, 12)     if not (x2 = x1) then         slope := (y2 - y1) / (x2 - x1)     end if     ang := arctand (slope)     locate (1, 1)     put "coords : ", x1, "/", y1, "/", x2, "/", y2     put "slope : ", slope     put "angle :", ang     drawline (x1, y1, x2, y2, 9)     delay (5)     View.Update     cls end loop

[Catalyst]

there some problems there
such as the negative angles and the fact and from 180 to 270 show as 0-90

[Homer_simpson]

lol well yeah... but it is fixable if you try to fix it... i have fixed it and used it in my new particle engine with gravity support which i'll upload in a few minutes...