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# Trigonometry

Videos and exercises on trigonometry. Watch the "Geometry" playlist first if you have trouble understanding the topics covered here.
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Graphs of trig functions
In this topic, we'll gain a deeper appreciation for the periodic nature of trig functions by visualizing and modeling real-world phenomena with them.
All content in “Graphs of trig functions”

### Graphs of trig functions

The unit circle definition allows us to define sine and cosine over all real numbers. Doesn't that make you curious what the graphs might look like? Well this tutorial will scratch that itch (and maybe a few others). Have fun.

### Modeling with periodic functions

By now, you are reasonably familiar with the graphs of sine and cosine and are beginning to appreciate that they can be used to model periodic phenomena. In this tutorial, you'll get experience doing just that--modeling with periodic functions!

### Long live tau

Pi (3.14159...) seems to get all of the attention in mathematics. On some level this is warranted. The ratio of the circumference of a circle to the diameter. Seems pretty pure. But what about the ratio of the circumference to the radius (which is two times pi and referred to as "tau")? Now that you know a bit of trigonometry, you'll discover in videos made by Sal and Vi that "tau" may be much more deserving of the throne!