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More Lessons for High School Regents Exam

Math Worksheets

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 θ = cos (90° - θ)

Secant and Cosecant are cofunctions because sec θ = csc 90° - θ)

Tangent and Cotangent are cofunctions because tan θ = cot 90° - θ)

**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°

The following figures give the cofunction identities. Scroll down the page for more examples and solutions on how to use cofunction identities.

**Cofunctions**

What is a cofunction?

Finding the cofunction.

Using the cofunction relationship

**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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