Tangent field : plotfield fieldplot

• Let f (t, y) be an expression depending of two variables t and y, then :
  plotfield(f(t,y),[t,y])
  draws the tangent field of the differential equation y' = f (t, y) where y is a real variable and where t is the abscissa,
• Let V be a vector of two expressions depending of 2 variables x, y but independant of the time t, then
  plotfield(V,[x,y])
  draws the vector field V,
• The range of values of t, y or of x, y can be specified with
  t=tmin..tmax, x=xmin..xmax, y=ymin..ymax
  in place of the variable name.
• The discretisation may be specified with optional arguments xstep=..., ystep=....

Input :

plotfield(4*sin(t*y),[t=0..2,y=-3..7])

Output :

Segments with slope 4*sin(t*y), representing tangents, are plotting in different points

With two variables x, y, input :

plotfield(5*[-y,x],[x=-1..1,y=-1..1])