The obvious answer is the relationships between the sides and angles of triangles. Waves in the sea are an example of a sine wave. Tidal Experts and Meterologists alike use sine waves to help predict tides. Music will also emit waves that may often look like a sine wave and pure notes will look like sine or cosine waves. The speed of a swinging pendulum can be plotted as a sine wave as well as the sound of a tuning fork.
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If you are in school and are studying trig then you are using trig in real life.
Surveying is all trig. Much trig in physics and engineering,
trig
cosine = adjacent/hypotenuse. It can be used as other trig functions can.
Trigonometry functions are used to work out the various properties of triangles.