Lab 7: Identities Crisis? What's in an identity? There are lots of relationships among the trigonometric functions, and you've already worked with several identities. Most important Is sin2 0 + cos20 = 1 Sometimes referred to as the basic trig identity or the Pythagorean Identity, this Identity Is often used to create or validate other formulas. Why is this called the Pythagorean Identity? 1. Show how you could use the basic identity above to write a new formula for tan 0 using only the cos 0. Remember you can rewrite the basic identity as either cos20 = 1 - sin20 or sin20 = 1 - cos20