Trigonometry is a branch ... is that these functions relate to each other through a great variety of intricate equations known as identities, equations that are always true. Each trigonometric ...

but many fail to make the leap on how crucial circles are for trig functions. With static graphs and equations, it's possible to get a handle on the rules of what various functions do and mean.

Yes, I just call it "trig" because I always misspell trigonometry. Maybe you can use the double angle formula and you don't have a problem with trig identities. It's very easy to do some of the ...