Question 1079666


reminder:

{{{x= r*cos(theta)}}}
{{{y= r*sin(theta)}}}

if
{{{x^2+y^2=25}}}, than we have

{{{(r*cos(theta))^2+( r*sin(theta))^2=25}}}

{{{r^2*cos^2(theta)+ r^2*sin^2(theta)=25}}}

{{{r^2(cos^2(theta)+ sin^2(theta))=25}}}

{{{r^2(1)=25}}}

{{{r^2=25}}}

{{{r=5}}}

answer:
B.) {{{ r=5 }}}