Use the Law of Cosines to prove that the distance between 2 polar points (r1, θ1) and (r2, θ2) is d2=r12+r22-2r1r2cos(θ2-θ1)

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- Nov 21st 2008, 10:50 AMrwc123Precal Proof for distance between 2 polar points
Use the Law of Cosines to prove that the distance between 2 polar points (r1, θ1) and (r2, θ2) is d2=r12+r22-2r1r2cos(θ2-θ1)

- Nov 21st 2008, 11:08 AMgalactus
Let be points in the plane.

Let

and

Sub these into the law of cosines, , gives the formula.