B Asking about integral notation

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TL;DR Summary
Why writing $$\int_{a}^{x} f(x) dx$$ is not correct?
Why should it be ##\int_{a}^{x} f(t)dt## ?

Couldn't it be like this:
Let F(x) = ##\int f(x)dx## so ##\int_{a}^{x} f(x)dx## = F(x) - F(a)

Thanks
 
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songoku said:
Summary: Why writing $$\int_{a}^{x} f(x) dx$$ is not correct?

Why should it be ##\int_{a}^{x} f(t)dt## ?

Couldn't it be like this:
Let F(x) = ##\int f(x)dx## so ##\int_{a}^{x} f(x)dx## = F(x) - F(a)

Thanks
The integral ##\displaystyle{\int_a^b f(t)\,dt}## is short for ##\displaystyle{\int_{t=a}^{t=b} f(t)\,dt}.## If you use the same letter (##b=t##) for two different meanings then you cause confusion.
 
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songoku said:
Summary: Why writing $$\int_{a}^{x} f(x) dx$$ is not correct?

Why should it be ##\int_{a}^{x} f(t)dt## ?

Couldn't it be like this:
Let F(x) = ##\int f(x)dx## so ##\int_{a}^{x} f(x)dx## = F(x) - F(a)

Thanks
Why is it not correct to write $$\sum_{k = 1}^k a_k$$
 
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Thank you very much for the explanation fresh_42 and PeroK
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Fermat's Last Theorem has long been one of the most famous mathematical problems, and is now one of the most famous theorems. It simply states that the equation $$ a^n+b^n=c^n $$ has no solutions with positive integers if ##n>2.## It was named after Pierre de Fermat (1607-1665). The problem itself stems from the book Arithmetica by Diophantus of Alexandria. It gained popularity because Fermat noted in his copy "Cubum autem in duos cubos, aut quadratoquadratum in duos quadratoquadratos, et...
I'm interested to know whether the equation $$1 = 2 - \frac{1}{2 - \frac{1}{2 - \cdots}}$$ is true or not. It can be shown easily that if the continued fraction converges, it cannot converge to anything else than 1. It seems that if the continued fraction converges, the convergence is very slow. The apparent slowness of the convergence makes it difficult to estimate the presence of true convergence numerically. At the moment I don't know whether this converges or not.

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