Serenus of Antinouplis (ca. 300 AD  ca. 360 AD) was an ancient Hellenistic mathematician.
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Serenus came either from Antinoeia or from Antinouplis, a city in Egypt founded by Hadrian. Two sources confirm that he was born in Antinouplis. It was once believed that he was born in Antissa, but this has been shown to have been based on an error.
Serenus wrote a commentary on the Conics of Apollonius, which is now lost. We hear from Theon of Symrna that the main result of the commentary was that of a number of angles that are subtended at a point on a diameter of a circle that is not the center, then with equal arcs of that circle, the angle nearer to the center is always less than the angle father away from the center.^{[1]} But he was also a prime mathematician in his own right, having written two works entitled On the Section of a Cylinder and On the Section of a Cone, works that came to be connected to Apollonius' Conics. This connection helped them to survive through the ages.
In the preface of On the Section of a Cylinder, Serenus states that his motivation for writing this work, as summarized by Heath, was that "many persons who were students of geometry were under the erroneous that the oblique section of a cylinder was different from the oblique section of a cone known as an ellipse, whereas it is of course the same curve."^{[1]} The work consists of thirtythree propositions.
In propositions one though fiftyseven of On the Section of a Cone, Serenus deals largely with the areas of triangular sections of right and scalene cones that are created by planes passing through the vertex. He shows when the area of a triangle of a certain class of triangles is at its maximum. Propositions fiftyeight through sixtynine form a separate section of the book and deal with the volumes of right right cones in relation to their heights, their bases and the areas of triangular sections through the axis.

