Question

formulas of identities

Answer 1

Defining relations for tangent, cotangent, secant, and cosecant in terms of sine and cosine. The Pythagorean formula for sines and cosines. This is probably the most important trig identity.

Answer 2

(a+b)^2
(a-b)^2
(a+b)(a-b)
(x+a)(x+b)