Could not find a theorem to solve this equation

[duelbuster]

Hello, I'm working on my essay about biomedical physics in vessels
There is an equation that I'm stuck to explain how it went from left side to right

or the general form is

I've tried all theorem I could think of (binomial etc.) and could not come to a conclusion.
Can you suggest the theorem so I can solve this equation, please?

 

[Cubist]

If you plug some numbers in you'll see that the LHS ≠ RHS

For the general form, it is approximately true (LHS≈RHS) for small values of x.

Try taking the reciprocal of the LHS of the general form, and find the first two terms of its Maclaurin series. Can you proceed from there?

 

[JeffM]

This is malpractice by someone. There is a difference between an equality and an approximation, and not knowing how accurate the approximation is under what restrictions renders a formula of approximation useless for any practical work.

[MATH]sin(x) = x[/MATH] is generally false.

[MATH]0 \text { degrees} \le |x| \le 0 \text { degrees } 15 \text { minutes} \implies \\ |sin(x) - x| < 0.0026 \implies sin(x) \approx x \text { for very small x}[/MATH].

 

[duelbuster]

This is malpractice by someone. There is a difference between an equality and an approximation, and not knowing how accurate the approximation is under what restrictions renders a formula of approximation useless for any practical work.

[MATH]sin(x) = x[/MATH] is generally false.

[MATH]0 \text { degrees} \le |x| \le 0 \text { degrees } 15 \text { minutes} \implies \\ |sin(x) - x| < 0.0026 \implies sin(x) \approx x \text { for very small x}[/MATH].

Thank you. Since I've read that equation from a (low ranking) published paper that vaguely described.
This equation is likely to be malpractice by that writer as you said.