What is the Use of the Constant in the Integral?

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SUMMARY

The discussion centers on the mathematical function defined by the integral $$f(x)=\int_{t=p}^{t=x} \frac{\cos t}{t} dt$$, specifically addressing the constant added to the integral. Participants clarify that if the integral starts at p=3, then the integral evaluates to 0 at x=3, necessitating the identification of the constant. The correct derivative is also confirmed as $$f'(x) = \frac{\cos x}{x}$$, with the condition that f(3) = 4, leading to the conclusion that the function can be expressed in the form of the integral with the appropriate constant added.

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Homework Statement
Find f(x) where ##f(x)=\frac{\cos x}{x}## and f(3) = 4. State the answer in form of ##f(x)=\int_{t=p}^{t=q} (........)##
Relevant Equations
Fundamental Theorem of Calculus
This is my attempt:
$$f(x)=\int_{t=p}^{t=x} \frac{\cos t}{t} dt$$

But I am not sure what ##p## is and what the use of ##f(3)=4##

Thanks
 
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You forgot about the constant that is added to the integral. If you start the integral at p=3, then you know that the integral part is 0 at x=3. So what constant is added to the integral?
 
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songoku said:
Homework Statement:: Find f(x) where ##f(x)=\frac{\cos x}{x}## and f(3) = 4. State the answer in form of ##f(x)=\int_{t=p}^{t=q} (...)##
Did you forget to add the prime? Shouldn't it be ##f'(x) = \frac{\cos x}{x}##?
 
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FactChecker said:
You forgot about the constant that is added to the integral. If you start the integral at p=3, then you know that the integral part is 0 at x=3. So what constant is added to the integral?
I understand

Mark44 said:
Did you forget to add the prime? Shouldn't it be ##f'(x) = \frac{\cos x}{x}##?
Yes, I am sorry

Thank you very much FactChecker and Mark44
 

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