Question 1134426
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r = {{{cos(2theta)}}}


r = {{{cos^2(theta)}}} - {{{sin^2(theta)}}}


r = {{{(x/r)^2}}} - {{{(y/r)^2}}}


{{{r^3}}} = {{{x^2}}} - {{{y^2}}}


{{{(x^2 + y^2)^(3/2)}}} = {{{x^2}}} - {{{y^2}}}.


Or, if you want to avoid radicals, square both sides


{{{(x^2 + y^2)^3}}} = {{{(x^2 - y^2)^2}}}.
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