How do you find the polar coordinate of the following point (-2, 5)?

1 Answer
Jan 9, 2016

If (a,b)(a,b) is a are the coordinates of a point in Cartesian Plane, uu is its magnitude and alphaα is its angle then (a,b)(a,b) in Polar Form is written as (u,alpha)(u,α).
Magnitude of a cartesian coordinates (a,b)(a,b) is given bysqrt(a^2+b^2)a2+b2 and its angle is given by tan^-1(b/a)tan1(ba)

Let rr be the magnitude of (-2,5)(2,5) and thetaθ be its angle.
Magnitude of (-2,5)=sqrt((-2)^2+5^2)=sqrt(4+25)=sqrt29=r(2,5)=(2)2+52=4+25=29=r
Angle of (-2,5)=Tan^-1(5/(-2))=Tan^-1(-5/2)=-68.198(2,5)=tan1(52)=tan1(52)=68.198 degree

implies Angle of (-2,5)=-68.198(2,5)=68.198 degree

But since the point is in second quadrant so we have to add 180180 degree which will give us the angle.

implies Angle of (-2,5)=-68.198+180=111.802(2,5)=68.198+180=111.802

implies Angle of (-2,5)=111.802=theta(2,5)=111.802=θ

implies (-2,5)=(r,theta)=(sqrt29,111.802)(2,5)=(r,θ)=(29,111.802)
implies (-2,5)=(sqrt29,111.802)(2,5)=(29,111.802)
Note that the angle is given in degree measure.