The polar coordinates are (r,φ), where r=[tex] \sqrt{x^2+y^2} [/tex] and cosφ=[tex] \frac{x}{ \sqrt{x^{2} +y^{2} } } [/tex], sinφ=[tex] \frac{y}{ \sqrt{ x^{2} + y^{2} } } [/tex].
So, when we are counting r, we obtain that r=[tex] \sqrt{ x^{2} + y^{2} } = \sqrt{(5cos(theta))^{2}+(5sin(theta))^{2}} = [/tex]=[tex] \sqrt{25(cos(theta)^{2}+sin(theta)^{2}) } =\sqrt{25}=5 .[/tex]
That's why the polar form of the parametric equations is r=5 (the circle of radius 5) and the right answer is B.
