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# 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])

giac documentation written by Renée De Graeve and Bernard Parisse