What is the equation of a limacon?

1 Answer
A. S. Adikesavan
Apr 27, 2016

#r^2=a^2 cos 2theta#.
The graph is the fallen eight, looking like the symbol #oo#...

Explanation:

For the double loop of #r^2=a^2 cos 2theta, cos 2theta >=0#.

So, the range for #theta in [0, 2pi]# excludes #(pi/4, (3pi)/4)# and

#((5pi)/4, (7pi)/4)#, Here, #cos 2theta < 0#...

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