Finding domain of a trigonometric function

In summary, the domain of the function $$f(x) = \frac{1+x}{ e^{cos(x)}}$$ is all real numbers, as both the numerator and denominator are defined for all values of x and the denominator is never equal to 0.
  • #1
tmt1
234
0
I need to find the domain of this function:

$$f(x) = \frac{1+x}{ e^{cos(x)}}$$

I set $${ e^{cos(x)}}> 0$$

But I'm not sure what to do after this.
 
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  • #2
tmt said:
I need to find the domain of this function:

$$f(x) = \frac{1+x}{ e^{cos(x)}}$$

I set $${ e^{cos(x)}}> 0$$

But I'm not sure what to do after this.

The top is obviously defined for all x.

The bottom, as you have established, is always positive. As both cos(x) and e^x are defined for all x, so is their composition.

So the top and bottom are defined for all x. The only place where the quotient of the two functions might not be defined is where the denominator is 0. But you already established that this doesn't happen anywhere.

So what is the domain of your function?
 
  • #3
Prove It said:
The top is obviously defined for all x.

The bottom, as you have established, is always positive. As both cos(x) and e^x are defined for all x, so is their composition.

So the top and bottom are defined for all x. The only place where the quotient of the two functions might not be defined is where the denominator is 0. But you already established that this doesn't happen anywhere.

So what is the domain of your function?

All real numbers?
 
  • #4
tmt said:
All real numbers?

Correct :)
 
  • #5


As a scientist, it is important to understand the domain of a function in order to properly analyze and interpret its behavior. In this case, the domain of the function f(x) can be determined by considering the restrictions on the input values that would result in a meaningful output.

Since the function involves a trigonometric function (cos(x)) and an exponential function (e^x), we need to consider the restrictions on the input values for both of these functions. The cosine function has a domain of all real numbers, while the exponential function has a domain of all real numbers as well. However, the output of the exponential function is always positive, meaning that the fraction in the function f(x) will only be defined for values of x that result in a positive output for the exponential function.

Therefore, the domain of the function f(x) can be written as:
$$
\boxed{ \{ x \in \mathbb{R} \mid e^{cos(x)} > 0 \} }
$$

In other words, the domain of the function f(x) is all real numbers except for the values of x that result in a negative or zero output for the exponential function, which would make the fraction undefined. This can also be written as:
$$
\boxed{ \{ x \in \mathbb{R} \mid cos(x) \neq ln(0) \} }
$$

Overall, understanding the domain of a function is crucial for analyzing its behavior and making accurate conclusions. By considering the restrictions on the input values for each component of the function, we can determine the valid domain for the function f(x).
 

FAQ: Finding domain of a trigonometric function

What is the domain of a trigonometric function?

The domain of a trigonometric function is the set of all possible input values for which the function is defined. In other words, it is the set of values that we can plug into the function to get a valid output.

How do you determine the domain of a trigonometric function?

To determine the domain of a trigonometric function, we need to consider any restrictions on the input values. These restrictions may include: the function being undefined at certain values, the function having a limited range of values, or the function being defined only for certain types of numbers (e.g. real numbers, integers, etc.).

What are the common types of trigonometric functions and their domains?

The most common types of trigonometric functions are sine, cosine, tangent, cotangent, secant, and cosecant. The domain for these functions is typically all real numbers, except for certain values that would result in undefined outputs (e.g. dividing by zero). For example, the domain of the sine function is all real numbers, while the domain of the tangent function is all real numbers except for multiples of π/2.

Can the domain of a trigonometric function be restricted?

Yes, the domain of a trigonometric function can be restricted by adding additional conditions or limitations to the input values. For example, we can restrict the domain of the tangent function to only positive real numbers by including the condition that the input must be greater than 0. This would result in a restricted domain of (0, ∞).

How can finding the domain of a trigonometric function be useful?

Finding the domain of a trigonometric function is important in many applications of trigonometry, such as in solving equations, graphing functions, and understanding the behavior of a function. It allows us to identify any limitations or restrictions on the input values, and helps us to determine when the function is valid and when it is not.

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