(x,y)->(r,theta);(r,theta)=(sqrt(x^2+y^2),tan^-1(y/x))(x,y)→(r,θ);(r,θ)=(√x2+y2,tan−1(yx))
r=sqrt(x^2+y^2)=sqrt(11^2+(-9)^2)=sqrt(121+81)=sqrt202~~14.2r=√x2+y2=√112+(−9)2=√121+81=√202≈14.2
theta=tan^-1(-9/11)θ=tan−1(−911)
However, (11,-9)(11,−9) is in quadrant 4, and so we must add 2pi2π to our answer.
theta=tan^-1(-9/11)+2pi ~~5.60^cθ=tan−1(−911)+2π≈5.60c
(sqrt202,tan^-1(-9/11)+2pi) or (14.2,5.60^c)(√202,tan−1(−911)+2π)or(14.2,5.60c)