Given f(x)=cos c and g(x)=cot x, what are the domain and range of f(g(x))?

Answer choices:

A. Domain: All real numbers; Range: all real numbers.

B. Domain: All real numbers x except x does not equal npi for all integers n; Range: all real numbers.

C. Domain: All real numbers x except x does not equal npi for all integers n; Range: -1 is less than or equal to y is less than or equal to 1.

D. Domain: All real numbers; Range: -1 is less than or equal to y is less than or equal to 1.

Respuesta :

Answer:

Option C

Step-by-step explanation:

We know that the function [tex]y = cos(x)[/tex] has as its domain all real numbers, and as a range [tex]-1\leq y\leq 1[/tex]

 We know that the function [tex]cot(x) = \frac{cos(x)}{sin(x)}[/tex]

The denominator of the function can not be equal to 0. But [tex]sin(x) = 0[/tex] for all [tex]x = n\pi[/tex] where n is an integer number.

Therefore the domain of cot(x) are all real numbers except [tex]x = n\pi[/tex]

The range of cot(x) are all real numbers

Then, the domain of f(g(x)) is:

x ∈ Domain g and g(x) ∈ Domain of f

Where:

Domain of g: All reals except [tex]x = n\pi[/tex]

Domain of f: All reals.

This is:

Domain of f(g(x)):

All real numbers except [tex]n\pi[/tex]

Range of f(g(x)):

 [tex]-1\leq y\leq 1[/tex]

Therefore the correct option is:

C. Domain: All real numbers x except x does not equal npi for all integers n; Range: -1 is less than or equal to and is less than or equal to 1.