Understanding the Differences between Integrating and Taking the Square Root

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    Calc 1
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Discussion Overview

The discussion revolves around the differences between integrating a function and taking the square root of an integral, specifically examining the expressions $$\int \sqrt{f(x)}dx$$ and $$\sqrt{\int f(x)dx$$. Participants explore whether these two operations yield equivalent results and seek to understand the underlying reasons for any differences.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • Some participants assert that $$\int \sqrt{f(x)}dx$$ is not equivalent to $$\sqrt{\int f(x)dx$$, citing specific examples to illustrate this point.
  • One participant provides a more complex example involving constants and variables, questioning the equivalence of $$\sqrt{(C\int\sqrt{(a+b)}dx)^2}$$ and $$\sqrt{C^2\int(a+b)dx$$.
  • Another participant suggests testing with a specific function, $$f(x)=x^2$$, to demonstrate the non-equivalence of the two expressions.
  • A participant explains the relationship between definite integrals and sums, noting that $$\sqrt{a+b} \neq \sqrt{a} + \sqrt{b}$$ in most cases, which supports the argument that $$\sqrt{\int_a^bf(x)\ dx} \neq \int_a^b\sqrt{f(x)}\ dx$$.
  • One participant expresses appreciation for the clarification provided regarding the differences between the operations.

Areas of Agreement / Disagreement

Participants generally agree that the two operations are not equivalent, although the discussion includes various examples and reasoning to support this view. There is no consensus on a singular explanation, as different participants provide distinct perspectives on the matter.

Contextual Notes

The discussion touches on the limitations of applying square root and integral operations interchangeably, emphasizing the need for careful consideration of the mathematical properties involved. However, specific assumptions and definitions are not fully explored.

iScience
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$$\int \sqrt{f(x)}dx$$ is NOT the same as..

$$\sqrt{\int f(x)dx}$$ right?

i did an example problem and they turned out not to be equivalent but i just wanted to make certain.




if they actually aren't equivalent.. why aren't they?
 
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well, better example:

$$\sqrt{(C\int\sqrt{(a+b)}dx)^2}$$

this is not the same as..

$$\sqrt{C^2\int(a+b)dx}$$

is it?

(C= constant, a= variable, b=constant (not that it really matters..))
 
Last edited:
iScience said:
$$\int \sqrt{f(x)}dx$$ is NOT the same as..

$$\sqrt{\int f(x)dx}$$ right?

i did an example problem and they turned out not to be equivalent but i just wanted to make certain.




if they actually aren't equivalent.. why aren't they?

Try ##f(x)=x^2## and you'll see for yourself why they are not the same.
 
Remember that the definite integral is a kind of sum (technically a limit of sums), and so one way to understand why things may or may not work with the integral is to compare it to a sum.

In this case, if you remember that ##\sqrt{a+b}\neq\sqrt{a}+\sqrt{b}## most of the time, and in general ##\sqrt{\sum_1^n a_i}\neq\sum_1^n\sqrt{a_i}##, it's not too hard to see why, most of the time, ##\sqrt{\int_a^bf(x)\ dx}\neq\int_a^b\sqrt{f(x)}\ dx##.
 
gopher_p said:
Remember that the definite integral is a kind of sum (technically a limit of sums), and so one way to understand why things may or may not work with the integral is to compare it to a sum.

In this case, if you remember that ##\sqrt{a+b}\neq\sqrt{a}+\sqrt{b}## most of the time, and in general ##\sqrt{\sum_1^n a_i}\neq\sum_1^n\sqrt{a_i}##, it's not too hard to see why, most of the time, ##\sqrt{\int_a^bf(x)\ dx}\neq\int_a^b\sqrt{f(x)}\ dx##.


Thanks this was helpful! :)
 

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