A dozen of angle trisection methods using limacon of Pascal[1] are known, and one more such a method is shown in Fig.1.
Fig.1
Let 
be the given angle to be trisected. We draw line OC which bisects
, therefore
. Line OC intersects the limacon
( red loop ) at point D.
Limacon of Pascal[2] is defined in the polar coordinates by the equation
We use only the little loop of the limacon (1) , enlarged by factor 2, mirrored with respect to the y-axis, and shifted 1 unit to the right along the x-axis. Such a transformed limacon is defined in the rectangular coordinates by the following parametric equations
where 
, and 
is the bisector of the given angle 
to be
trisected.
At point D on both sides of line OC we draw lines DE and DF which make 
with line
OC . Points E and F trisect , and 
is equilateral.
In order to prove the above statements it suffices to show that 
. Let us denote
by 
, and 
by
. The Law of Sines for 
yields
From equations (2) and relation 
, follows
From (3) and (4) follows
and finally we obtain 
.
The presented trisection method can be generalized for the angle n-section, see Fig.2.
Fig.2
In Fig.2 angle 
is the half of the vertex angle of a regular n-gon. The Law of Sines for
in Fig.2 yields
From (5) and Fig.2 we obtain following equations
Next we show that equations (6) represent a special case of an epitrochoid[3]. An epitrochoid is defined by the following parametric equations
For the special case a = 1, and h = a+b, from (7) follows
Making in (8) the substitution
we obtain
Comparing (6) and (10), it follows that (6) can be obtained from (10) for 
, or
and by scaling (10) with the factor
[1] Loy, J. "Trisection of an Angle" http://www.jimloy.com/geometry/trisect.htm
[2] Eric W. Weisstein. "Limacon" http://mathworld.wolfram.com/Limacon.html
[3] Eric W. Weisstein. "Epitrochoid" http://mathworld.wolfram.com/Epitrochoid.html
See also:
Avni Pllana "Approximate Angle Trisection and N-Section" (PDF)
Avni Pllana "Approximate Angle Trisection" (PDF)
Avni Pllana "Approximate Construction of Heptagon and Nonagon" (PDF)
Avni Pllana "Three Concurrent Lines" (PDF)
Avni Pllana "A Generalization of Ceva's Theorem for Tetrahedron" (PDF)
Avni Pllana "A Generalization of the Nagel Point" (PDF)
Avni Pllana "An Interesting Triangle Center" (PDF)
Avni Pllana "A Derivation of Mollweide Equations" (PDF)
Avni Pllana "Miscellaneous Results on Tetrahedron" (PDF)
Avni Pllana "A Proof of Pythagoras' Theorem" (PDF)
Avni Pllana "Some results on tangential triangle" (PDF)
Avni Pllana "Some results on side-bisector reflected triangle" (PDF)
Avni Pllana "Circle Connections" (PDF)
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Avni Pllana "Eagle Theorem" (PDF)
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Avni Pllana "Some results on orthopolars for a given point" (PDF)
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Avni Pllana "Determinants of nonsquare matrices" (PDF)