What is the domain of the sine and cosine functions?
the set of all real numbers.
What is the domain of the tangent and secant function?
The set of all real numbers, except odd integer multipliers of
What is the difinition of an identity?
Two functions f and g are said to be identically equalÂ if: f(x)=g(x) for every value of x for which both functions are defined. Such an equation is reffered to as an identity. (An equation that is not an identity is called a conditional equation.