How do you convert x^2+y^2 - 2y=0x2+y22y=0 into polar form?

1 Answer
Jul 13, 2016

Make use of a few conversion formulas and simplify. See below.

Explanation:

Recall the following formulas, used for conversion between polar and rectangular coordinates:

  • x^2+y^2=r^2x2+y2=r2
  • rsintheta=yrsinθ=y

Now take a look at the equation:
x^2+y^2-2y=0x2+y22y=0

Since x^2+y^2=r^2x2+y2=r2, we can replace the x^2+y^2x2+y2 in our equation with r^2r2:
x^2+y^2-2y=0x2+y22y=0
->r^2-2y=0r22y=0

Also, because y=rsinthetay=rsinθ, we can replace the yy in our equation with sinthetasinθ:
r^2-2y=0r22y=0
->r^2-2(rsintheta)=0r22(rsinθ)=0

We can add 2rsintheta2rsinθ to both sides:
r^2-2(rsintheta)=0r22(rsinθ)=0
->r^2=2rsinthetar2=2rsinθ

And we can finish by dividing by rr:
r^2=2rsinthetar2=2rsinθ
->r=2sinthetar=2sinθ