How do you graph r=3+2costhetar=3+2cosθ?

1 Answer
Jul 23, 2018

See the graph of this dimpled limacon and details.

Explanation:

This limacon r = 3 + 2 cos theta in [ 1, 5 ]r=3+2cosθ[1,5].

The pole r = 0 is outside.

As r is f ( cos theta ) = f ( cos (- theta ))#, the graph is symmetrical

about the initial line theta = 0θ=0.

Use r = sqrt ( x^2 + y^2 ) >= 0r=x2+y20

and r (cos theta. sin theta ) = ( x, y )r(cosθ.sinθ)=(x,y), for the Cartesian form

( x^2 + y^2 ) - 3 sqrt ( x^2 + y^2 ) - 2 x =0(x2+y2)3x2+y22x=0

The Socratic graph of this dimpled limacon is immediate.
graph{ ( x^2 + y^2 ) - 3 sqrt ( x^2 + y^2 ) - 2 x =0}