SOLUTION: convert the equation from polar to rectangular {{{r=cos(2theta)}}}

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Question 1134426: convert the equation from polar to rectangular
r=cos%282theta%29
Answer by ikleyn(52809) About Me  (Show Source):
You can put this solution on YOUR website!
.
r = cos%282theta%29


r = cos%5E2%28theta%29 - sin%5E2%28theta%29


r = %28x%2Fr%29%5E2 - %28y%2Fr%29%5E2


r%5E3 = x%5E2 - y%5E2


%28x%5E2+%2B+y%5E2%29%5E%283%2F2%29 = x%5E2 - y%5E2.


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


%28x%5E2+%2B+y%5E2%29%5E3 = %28x%5E2+-+y%5E2%29%5E2.