Exact differential equation test
partials(m,n)
Prgm
@m(x,y),n(x,y)
ClrIO
@ToDo: allow them to differ by constants
If d(m,y)=d(n,x) Then
Pause d(m,y)
Pause [["M:"&string(expand(
∫(m,x)))&"+c(y)"]["N:"&string
(expand(∫(n,y)))&"+c(x)"]]
Else
Disp "Not exact"
EndIf
EndPrgm
Angle of parallelism for a given distance
ang(dist)
Func
@angle of || for a given
distance
Return 2*tan-1(e^(-dist))
EndFunc