MHB How to simplify a diabolical expression involving radicals

AI Thread Summary
The discussion focuses on simplifying a complex expression involving radicals, which equals 1/2. Various substitutions, including x = √5 and x = 2√5, have been attempted without success. A suggested substitution is u = √(5 + 2√5), which may help simplify the expression further. This approach allows for rewriting parts of the expression, potentially making it easier to simplify. The goal remains to analytically simplify the original diabolical expression.
kalish1
Messages
79
Reaction score
0
A friend and I have been working on this problem for hours - how can the following expression be simplified analytically?

It equals $\frac{1}{2},$ and we have tried the following to no avail:

1. Substitution of $x = \sqrt{5}$
2. Substitution of $x = 2\sqrt{5}$
3. Substitution of $x = 5+\sqrt{5}$
4. Substitution of $x = \sqrt{5 + \sqrt{5}}$

Here goes:
$$\dfrac{\dfrac{\sqrt{5 + 2\sqrt{5}}}{2} + \dfrac{\sqrt{5(5 + 2\sqrt{5})}}{4} - \dfrac{\sqrt{10 + 2\sqrt{5}}}{8}}{\dfrac{\sqrt{5(5 + 2\sqrt{5})}}{4} + 5 \cdot \dfrac{\sqrt{5 + 2\sqrt{5}}}{4}}$$

Thanks in advance for any help.

This question has been crossposted here - fractions - How to simplify a diabolical expression involving radicals - Mathematics Stack Exchange
 
Mathematics news on Phys.org
Try the substitution $u = \sqrt{5 + 2 \sqrt{5}}$. Then you have:
$$\sqrt{5(5 + 2 \sqrt{5})} = \sqrt{5} u$$
$$\sqrt{10 + 2 \sqrt{5}} = \sqrt{u^2 + 5}$$
You'll still have a root but you'll be able to simplify the fraction I think.
 
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
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...
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...

Similar threads

Replies
41
Views
5K
Replies
2
Views
1K
Replies
1
Views
2K
Replies
15
Views
2K
Replies
3
Views
1K
Replies
1
Views
8K
Replies
6
Views
2K
Replies
3
Views
1K
Replies
3
Views
1K
Replies
2
Views
2K
Back
Top