Winplot  1.5MB exe file, no install.

good for graphing non-function equations
(functions too)

Window    maximize
 2-dim     maximize

 Equa
  1. Explicit...
      f(x)=  x^2  sqrt(x)  sin(x)  log(x)  ln(x)  e  pi ...

  3. Implicit...   equations
      x^2+y^2=1

   Point  (x,y)
   Segment   (x1,y1) to (x2.y2)

 Equa
   Inventory      Ctrl+I
    dupl  (copy and paste)
    edit   Color    pen width  solid/dashed/dotted

Arrows to move graph left right up down.
PgUp zooms in
PgDn zooms out
If zoom out, might need to View | view ??????

 View  Grid...  on/off: axes,ticks,X Y interval("scale") pi/2
            "rectangular" for gridlines
            "border" for scales 
 View Axes on/off
View |Set corners to x y 

One | Zeros... 

Saves as a .wp2 file