The image on the right shows the de Lacy Bridge in Drogheda, Co - Leaving Cert DCG - Question B-2 - 2019

Using the vertex at B as a reference point, construct the parabola by determining the focal distance. Use the formula for the parabola, which states that for any point (x, y) on the curve, the distance from the point to the focus is equal to the distance from the point to the directrix. Calculate and plot specific points along the curve based on this relationship.

Using the points constructed in the previous steps, sketch the curve ABC. Ensure that the curve is smooth and follows the parabolic shape as described in the instructions.

Draw the rectangular outline for the curve DEF using reference points from the diagram. Start by locating vertices at points E and F based on the description of the double hyperbola.

To find points on the upper half of the left-hand hyperbola, utilize the focal points and corresponding asymptotes. Measure distances accurately to ensure the hyperbola matches the given plan.

Once the upper half is established, reflect the shape across the central axis to create the lower half of the hyperbola.

Using the points plotted from the upper and lower halves, draw a clean curve for DEF ensuring that it accurately represents the sections of the double hyperbola.

For the right-hand side (RHS), reflect the previously drawn curves to ensure symmetry in your diagram.

Indicate the central roadway situated in the diagram. Ensure to incorporate any hidden lines accurately.

Identify and draw line GH, ensuring it corresponds with the given elevations. Accurately draw the three corresponding lines as per the instructions.

Using a compass, establish the centers for the arcs needed in the design based on the intersection points of the hyperbola and the roadway.

Finalize the drawing by ensuring all projected lines and arcs are accurately depicted according to the specifications.

In the elevation, mark the location of the focus of the parabola ABC, which is positioned 4.9 m from vertex B.

Construct a line that will touch the parabola at the point C, ensuring that it is correctly aligned to be tangential to the curve.

Once the tangent line has been determined, draw it clearly on the diagram, ensuring it meets the parabola at point C.