The 41st parallel is a circle of latitude. A circle of latitude is an imaginary east-west circle on Earth. Circles of latitude are often called parallels because they are parallel to each other.

It should be noted that during either equinox, every location in the world receives equal amounts of daylight and darkness, not just the northern hemisphere.

Some people say that the best fishing in the world can be done in water sources located on the 41^st parallel. If you're an avid reader or an avid fisher, you might want to check out the book Fly Fishing the 41^st: Around the World on the 41^st Parallel. The book tells the tale of a man who travels around the world, fishing along the 41st parallel.

Sample answer:

The tides of the ocean can be modeled by sine waves since they come up and go down in a repeating pattern. The motion of water, light, sound, and seismic waves from an earthquake can be modeled by sine waves because they travel in waves. Oscillation such as a spring bouncing back and forth or something swinging on a rope is periodic and can be modeled by sine waves. Sunrise and sunset times are related to the hours of daylight discussed in Example 6 and can also be modeled by sine waves.