Definite integral with complex result?

In summary, the integral ∫ 3+ x√x from -1 to 4 is not well-defined due to the domain restriction of the square root function. The given solution attempts to evaluate the integral but is not correct. A proper statement of the problem is needed in order to find a valid solution.
  • #1
Painguy
120
0

Homework Statement


∫ 3+ x√x from -1 to 4


Homework Equations





The Attempt at a Solution


∫ 3+ x√x from -1 to 4 = 3x+(2(x^5/2))/5 evaluated from -1 to 4

(12 + (2(4^5/2))/5) +(3 +(2(-1)^5/2)/5) ?

15+64/5 +(2(-1^(5/2))/5)

139/5 -(2(-1^(5/2)))/5

139/5 -2i/5

is that right?
 
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  • #2
Painguy said:

Homework Statement


∫ 3+ x√x from -1 to 4


Homework Equations





The Attempt at a Solution


∫ 3+ x√x from -1 to 4 = 3x+(2(x^5/2))/5 evaluated from -1 to 4

(12 + (2(4^5/2))/5) +(3 +(2(-1)^5/2)/5) ?

15+64/5 +(2(-1^(5/2))/5)

139/5 -(2(-1^(5/2)))/5

139/5 -2i/5

is that right?

Yes:

http://www.wolframalpha.com/input/?i=integrate+3+++x*sqrt(x)+from+-1+to+4
 
  • #3
Painguy said:

Homework Statement


∫ 3+ x√x from -1 to 4
Because of the term with the square root, the integrand is defined only for x ≥ 0. What is the complete statement of the problem?

Although there is a version of the square root function whose domain includes negative numbers, this is usually not presented in calculus courses.
Painguy said:

Homework Equations





The Attempt at a Solution


∫ 3+ x√x from -1 to 4 = 3x+(2(x^5/2))/5 evaluated from -1 to 4

(12 + (2(4^5/2))/5) +(3 +(2(-1)^5/2)/5) ?

15+64/5 +(2(-1^(5/2))/5)

139/5 -(2(-1^(5/2)))/5

139/5 -2i/5

is that right?
 

1. What is a definite integral with complex result?

A definite integral with complex result is an integration problem where the integral evaluates to a complex number. This means that the result of the integral will have a real and imaginary component.

2. How is a definite integral with complex result different from a regular definite integral?

A regular definite integral evaluates to a real number, while a definite integral with complex result evaluates to a complex number. This is because the function being integrated may have complex values, or the limits of integration may be complex numbers.

3. What are some examples of functions that can result in a definite integral with complex result?

Functions that have complex values, such as trigonometric functions like sine and cosine, can result in a definite integral with complex result. Additionally, functions with complex exponents, such as e^z, can also lead to a complex result.

4. How is a definite integral with complex result useful in science?

A definite integral with complex result can be useful in solving complex physics and engineering problems, as well as in signal processing and control systems. It can also be used in probability and statistics to calculate complex probabilities.

5. How can one evaluate a definite integral with complex result?

To evaluate a definite integral with complex result, one can use the same techniques as for regular definite integrals, such as the fundamental theorem of calculus, substitution, and integration by parts. However, it is important to keep track of the real and imaginary components separately and use complex arithmetic when necessary.

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