Find Cartesian form of equation r=9cos (theta)?

2 Answers
Jun 26, 2018

x2+y29x=0

Explanation:

we need the rectangular Polar transformations

r2=x2+y2

x=rcosθ

y=rsinθ

we have

r=9cosθ

multiply by r

r2=9rcosθ

using the transformations above

x2+y2=9x

x2+y29x=0

Jun 26, 2018

x29x+y2=0

Explanation:

to convert from polar to cartesian

xr=x2+y2

xx=rcosθcosθ=xr

r=9xr

multiply through by r

r2=9x

x2+y2=9x

x29x+y2=0

(x92)2+y2=814

which is the equation of a circle

centre =(92,0), radius =92