Area Between a Parabola and Two Tangent Lines

The goal of this note is to obtain the area enclosed between a parabola and two tangent lines using visual arguments. The first step that we have to follow, in order to do that, is noticing that the area between a parabola and a tangent line only depends on the leading coefficient of the quadratic function of the parabola. Finally, the intersection of two parabolas with the vertices on x-axis and equal leading coefficients is the key to obtain the result.