Co-Functions

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High School Math based on the topics required for the Regents Exam conducted by NYSED.

What are Cofunctions?
Cofunctions are pairs of trigonometric functions that have equal values when their arguments are complementary angles.
Sine and Cosine are cofunctions because $$\sin \theta = \cos \left( {90^\circ - \theta } \right)$$
Secant and Cosecant are cofunctions because $$\sec \theta = \csc \left( {90^\circ - \theta } \right)$$
Tangent and Cotangent are cofunctions because $$\tan \theta = \cot \left( {90^\circ - \theta } \right)$$

What are Cofunction Identities?
A function f is cofunction of a function g if f(A) = g(B) when A and B are complementary angles.
sin(A) = cos(B), if A + B = 90°
sec(A) = scs(B), if A + B = 90°
tan(A) = cot(B), if A + B = 90°

Cofunctions
What is a cofunction. Finding the cofunction. Using the cofunction relationship
Cofunctions

Cofunction Identities
This video explains the cofunction identities and how to determine cofunctions given a function value. Most cofunction values are verified on a calculator.
Cofunction Identities - Solving Trigonometric Equations
This video explains how to use cofunction identities to solve trigonometric equations.

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