Limacon is also called the Limacon of Pascal. It was first investigated by Dürer, who gave a method for drawing it in book Underweysung der Messung (1525). It was rediscovered by Étienne Pascal, father of Blaise Pascal, and named by Gilles-Personne Roberval in 1650 (MacTutor Archive).
3. The Limacon is a polar curve of the form having
Equation r=b+acosΘ
Cartesian Equation (x2 + y2 - 2ax)2 = b2(x2 + y2)
Some basic curves of limacon.
INTRODUCTION
5. Limacon is also called the Limacon of Pascal. It was
first investigated by Dürer, who gave a method for
drawing it in book Underweysung der
Messung (1525). It was rediscovered by Étienne
Pascal, father of Blaise Pascal, and named by Gilles-
Personne Roberval in 1650 (MacTutor Archive).
The word “Limacon" comes from the Latin limax,
meaning "snail."
HISTORY
6. As we know the equation of Limacon is r=b+acosѲ
In it, If,b>=2a the Limacon is convex.
If, 2a>b>a the Limacon is dimpled.
If, b=a the Limacon degenerates to a cardioid.
If, b<a the Limacon has an inner loop.
If, b=a/2 it is a trisectrix.
SOME BASIC CONDITIONS
7. The first one is the concaved.
Second one is dimpled.
The third one is cardioid.
CONSTRUCTION OF LIMACON
9. For , the inner loop has area.
=
=
=
where .
AREA OCCUPIED BY LIMACON
10. For , the outer loop has area
=
=
=
Area Contd.
11. Thus, the area between the loops is
But there is a special case for b = a/2
Area Contd.
12. In the special case of b=a/2 , these simplify to
Area Contd.
=
=
=
13. The parametric form of Limacon is:
x= (b + a cos t) cos t
y = (b + a cos t) sin t
gives the arc length s(t) as a function of t as
where E(z,k) is an elliptic integral of the second kind.
PARAMETRIC FORM
14. Let t=2𝜋 gives the arc length of the
entire curve as
where E(k) is a complete elliptic integral
of the second kind.
Contd.
15. Limacon Evolute means a limacon which is the locus of the
centre of curvature of another limacon. Some examples are,
LIMACON EVOLUTE
16. The catacaustic of a circle for a radiant point is the limacon
evolute.
It has parametric equations.
=
=
Contd.