Fundamental Trigonometric Identities

Question 1

What are the Reciprocal Identities?

Answer 1

csc x = 1/(sin x).
sec x = 1/(cos x).
cot x = 1/(tan x).

Question 2

What are the Tangent and Cotangent Ratio Identities?

Answer 2

tan x = sin x/cos x.

cot x = cos x/sin x.

Question 3

What are the Pythagorean Identities?

Answer 3

cos^2 x + sin^2 x = 1.
1 + tan^2 x = sec^2 x.
cot^2 x + 1 =csc^2 x.

Question 4

What are the Negative-Angle Identities?

Answer 4

sin(-x) = -sin x.
cos(-x) = cos x.
tan(-x) = -tan x.