This activity can be realized with TouchPlotLite (as well
of course as TouchPlot)
It is well known the curve with polar equation
is a conic with focal point the origin, parameter p,
excentricity e and focal axis the line with
ϕ angle to the horizontal axis.
It is even better to see it, adjusting the three parameters
p,e and ϕ...
Of course, parameters will have to be renamed a,b,c for use
- It is better to start with default values, so it might be
good to reset (bottom option on the main menu) touchplot to
- Go to Polar curve menu, and enter the formula :
It will be easier in 3.2 version of touchplot, but for now,
you need to use direct polish notation.
So the usual way to enter this formula would be : ÷, Vars,
a, +, 2nd, 1, ×, b, cos, −,
ϑ, Vars, c
(Not that long, nor difficult once you get the gripe on
- Validate with OK, and leave the defaults (minimum angle,
maximum, number of steps) as they are, from -π to π with
- Go back to Main menu, and now go to the Constants
sub-menu. Define minimum value for a parameter to be 0, and
leave the maximum at 5
Define minimum value for b to be 0 (for 0, you get a
circle...) and leave the maximum at 5
You can leave defaults minimum and maximum values for c or
change them to -3.14 and 3.14 if you prefer.
Activate the sliders for a,b and c parameters.
- Go back to main menu and go to the settings menu :
activate Lock aspect ration option, so that you'll keep
- Graph it, and move the sliders, observe...