rem                            AREA_3PT.CDL

rem        Copy Right by International Technology Transfer Corp.
rem        revision 1.0 7/30/99   


rem        Area of Triangle

rem        1. Select 3 points
rem        2. Calculate Area



clear
defopt = 2
acc = 0.00001

:start
getpos "Indicate First Point",defopt

on (@key + 3) goto exit, start,
defopt=@key
wx1 = @xworld
wy1 = @yworld
wz1 = @zworld

:second
getpos "Indicate Second Point",defopt

on (@key + 3) goto exit, start, second, 
defopt=@key
wx2 = @xworld
wy2 = @yworld
wz2 = @zworld

:third
getpos "Indicate Third Point",defopt

on (@key + 3) goto exit, second, third, 
defopt=@key
wx3 = @xworld
wy3 = @yworld
wz3 = @zworld

a = (wy2 - wy1) * (wz3 - wz1) - (wz2 - wz1) * (wy3 - wy1)
b = (wz2 - wz1) * (wx3 - wx1) - (wx2 - wx1) * (wz3 - wz1)
c = (wx2 - wx1) * (wy3 - wy1) - (wy2 - wy1) * (wx3 - wx1)
s = sqrt(a * a + b * b + c * c) / 2

pause "Area of Triangle = %.3fiPress Returnj", s

redraw
goto start
:exit