Sum Of The Interior Opposite Angles Of Cyclic Quadrilateral (Supplementary Angles)

In Euclidean geometry, a cyclic quadrilateral or inscribed quadrilateral is a quadrilateral whose vertices all lie on a single circle. This circle is called the circumcircle or circumscribed circle, and the vertices are said to be concyclic. The center of the circle and its radius are called the circumcenter and the circumradius respectively. Other names for these quadrilaterals are concyclic quadrilateral and chordal quadrilateral, the latter since the sides of the quadrilateral are chords of the circumcircle. 

A convex quadrilateral ABCD is cyclic if and only if its opposite angles are supplementary, that is, Angles
A+C = B+D= 180⁰

[muhammadIbrahim-kjpl]

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Please I don't know whether you made video tutorials of the following topics:
1.Bearing and distance
2.Probability
3. Complete circle geometry .
Please I need your kind response. Thank you