How do you convert 1=(-2x-3)^2+(y+9)^21=(2x3)2+(y+9)2 into polar form?

1 Answer
Dec 22, 2016

r^2(4cos^2theta+sin^2 theta)+6(2cos theta + 3 sin theta )+89=0r2(4cos2θ+sin2θ)+6(2cosθ+3sinθ)+89=0.., that can be reduced to the simple form 1/(4r)=1-sqrt3/2 cos theta14r=132cosθ, by shifting the origin to the focus at (-3/2, -9-sqrt3/2)(32,932).

Explanation:

The conversion formula is (x, y)=r(cos theta, sin theta)(x,y)=r(cosθ,sinθ).

Any reader can easily get thecomplicated polar form

r^2(4cos^2theta+sin^2theta)+6(2cos theta + 3 sin theta )+89=0r2(4cos2θ+sin2θ)+6(2cosθ+3sinθ)+89=0.

Interestingly, the given equation represents the ellipse

(x+3/2)^2/(1/2)^2+(y+3)^2/1^2=1(x+32)2(12)2+(y+3)212=1 that has center at (-3/2, -9), axes in e

directions of y-axis (for majoraxis) and x -axis.

Referring to a focus as pole ( origin shifted ), the polar equation

becomes as simple as l/r = 1/(4r)=1-sqrt3/2 cos thetalr=14r=132cosθ