What is the Cartesian form of r^2-4r = sin(theta) - 5 cos(theta) r24r=sin(θ)5cos(θ)?

1 Answer
Mar 2, 2016

4x^2+4y^2-5x+y=(x^2+y^2)^(3/2)4x2+4y25x+y=(x2+y2)32

Explanation:

To convert a polar coordinate (r,theta)(r,θ) in Cartesian form we use relation r=sqrt(x^2+y^2)r=x2+y2, rcostheta=xrcosθ=x, rsintheta=yrsinθ=y and theta=tan^(-1)(y/x)θ=tan1(yx). Using these relations

r^2−4r=sintheta−5costhetar24r=sinθ5cosθ cann be written as

r^3-4r^2=rsintheta−5rcosthetar34r2=rsinθ5rcosθ or

(x^2+y^2)^(3/2)-4(x^2+y^2)=y-5x(x2+y2)324(x2+y2)=y5x or

4x^2+4y^2-5x+y=(x^2+y^2)^(3/2)4x2+4y25x+y=(x2+y2)32