PlanarAngle

PlanarAngle[p->{q1,q2}] gives the angle between the half‐lines from p through q1 and q2.

PlanarAngle[{q1,p,q2}] gives the angle at p formed by the triangle with vertex points p, q1 and q2.

PlanarAngle[…,"spec"] gives the angle specified by "spec".

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