Construction of Parabola via Tangent Method:
Given the point A and B and the distance CD from AB to the vertex. Extend the axis CD and set off DE the same to CD. EA and EB are tangents to the parabola at A and B, respectively. Divide EA and EB into the similar number of equal parts or five here and number the division points as displayed in diagram.
Connect the corresponding points 1 and 1′, 2 and 2′, 3 and 3′ and so forth. These lines, as tangents of the required parabola form its envelope. Sketch the tangent curve.