We show a step-by-step procedure for obtaining the equation of the area of a portion of a circle above a chord (a.k.a. "Circular Segment") -- we denote this as Ac in the video -- at some level h. To solve this problem we rely on various tools, e.g. Doubling of portion of area in Quadrant I due to Symmetry, Setting up a Differential Rectangular Strip, the sine-squared/cosine-squared Trig. Identity, Trig. Substitution for evaluating an integral having a radical term, Double-Angle Formulas; moreover, we show how to deal with limits of integration when converting back from the angular variable in terms of the original rectangular y-dimension variable. At the end, we draw a schematic of a right triangle to show how to make proper angular-to-rectangular variable conversions.