Practical Geometry
 Quadrilateral: A quadrilateral is a foursided polygon.
For the given quadrilateral ABCD:

 Possible names of quadrilateral are ABCD, BCDA, CDAB and DABC.
 AB, CD and BC, DA are the pairs of opposite sides.
 AB, BC; BC, CD; CD, DA and DA, AB are the pairs of adjacent sides.
 A, C and B, D are the pairs of opposite vertices.
 AC and BD are the diagonals of quadrilateral ABCD.
 ∠A, ∠C and ∠B, ∠D are pairs of opposite angles.
 ∠B, ∠C; ∠A, ∠B; ∠C, ∠D and ∠D, ∠A are the pairs of adjacent angles.
For the given quadrilateral JKLM:

 Points lying in the interior of the quadrilateral are Q, R, S and O.
 Points lying in the exterior of the quadrilateral are V and U.
 Points lying on the boundary of th…
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