Verify That the Equation Is an Identity $$\frac { \cos ( x - y ) } { \cos ( x + y ) } = \frac { 1 + \tan x \tan y } { 1 - \tan x \tan y }$$

question 20

Essay

Verify that the equation is an identity.
- $$\frac { \cos ( x - y ) } { \cos ( x + y ) } = \frac { 1 + \tan x \tan y } { 1 - \tan x \tan y }$$

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Definitions:

Expression

A combination of symbols that represent values or operations in mathematics.

Z

Often represents a variable in mathematics or denotes the set of all integers in number theory.

Evaluate

To calculate the value of an algebraic expression by substituting variables with numerical values.

Expression

A combination of symbols that represent a value or relationship, often including numbers, variables, and operation symbols.