How do you convert $r=5costheta$ into rectangular equations?

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Answer 1 · 2017-01-20T08:20:39

$x^2+y^2-5x=0$

I take it that this means converting to Cartesian form. For conversion of Polar to and from Cartesian we use the eqns.

$r^2=x^2+y^2$

$x=rcostheta$
$y=rsintheta$

for
$r=5costheta$

multiply both sides by $r$

$r^2=5rcostheta$

using the above conversion eqns.

$x^2+y^2=5x$

$x^2+y^2-5x=0$

How do you convert r=5costhetar=5costheta into rectangular equations?