Watch the animation below to see how the Pythagorean Identity is really just the Pythagorean Theorem.
- sin (x)/sin2 x + cos2x == sin (x)/1 = sin (x)
- sin2 x+ cos2x /sin x == 1/sin x = csc (x)
- 1 - sin2(x) == cos2 (x)
- 1 - cos2(x) == sin2 (x)
We call it the Tangent Identity. It’s really just one of a bunch of plain old trig identities. But standardized tests like to slip it in.