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This is for my homies in maths class. I know many of you fear the sin & cos.

cosine is walking east-west, sine is walking north-south

They’re just a way to convert from circular coordinates to square coordinates.

radar-screen

polar coordinates "at sea" versus rectangular coordinates "in the city"

You want to get to the red dot. If you’re at sea you set your bearing θ and sail straight there. If you’re in the city you walk north and then east.

Cosine tells you how far you have to walk crosstown; sine is how far uptown.

 

That’s basically it. If you think uptown and crosstown look like legs of a right triangle, you’re thinking along the right track to understand where the many sin & cos formulæ come from.

Here’s a GPL'ed picture of why we sometimes think of cosine as a wave:

image

and sine:

image

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