Bridges are a type of infrastructure that are essential in transportation, often used to connect roadways across bodies of water. One can see many examples of reflectional symmetry in bridges. Engineers need to design bridges for safety and functionality, but many bridges are well-known for their aesthetics.

The Golden Gate Bridge in California and the Brooklyn Bridge in New York are two different kinds of suspension bridges.

The Golden Gate Bridge connects San Francisco to Marin County with a mile-long road. The bridge is made up of a deck that runs through two identical towers that rise out of the San Francisco Bay. Each tower is about a quarter of the distance from one end of the bridge to the other. A pair of main cables are anchored on the land, rise up to the first tower, connect to the second tower, and then are anchored on the land on the other side. The two cables run parallel to each other and connect to opposite sides of the towers.Between the two towers, the cables form a wide curve that opens up. The deck is held up by evenly spaced vertical cables that are attached to the main cables.

The Brooklyn Bridge connects Manhattan and Brooklyn. It also has a deck that runs through two identical towers that rise out of the East River. The deckholds a road for cars and a pedestrian walkway.The main cables begin and end like those on the Golden Gate Bridge, but the cable between the two towers dips to the deck. Like the Golden Gate Bridge, the deck is held up by evenly spaced vertical cables that are attached to the main cables. But there are additional cables that start at the top of the tower and are attached diagonally to the deck on both sides of each tower.

Respond to the following prompts in a short paragraph.

1. What kind of symmetry is evident in these bridges?

2. From what angles do you see symmetry in these, or other bridges?

3. Why is symmetry important in a bridge?