How do you convert x^2 + y^2 = 4x + 4yx2+y2=4x+4y to polar form?

1 Answer
Oct 15, 2016

r=4costheta+4sinthetar=4cosθ+4sinθ

Explanation:

x=rcosthetax=rcosθ
y=rsinthetay=rsinθ
LHS=x^2+y^2=r^2cos^2theta+r^2sin^2theta=r^2(cos^2theta+sin^2theta)=r^2LHS=x2+y2=r2cos2θ+r2sin2θ=r2(cos2θ+sin2θ)=r2
As cos^2theta+sin^2theta=1cos2θ+sin2θ=1
RHS=4rcostheta+4rsintheta=4r(cos theta+sintheta)RHS=4rcosθ+4rsinθ=4r(cosθ+sinθ)
LHS=RHS
r^2=4r(costheta+sintheta)r2=4r(cosθ+sinθ)
Finally r=4(costheta+sintheta)r=4(cosθ+sinθ)