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# Why does physicist cancel out differentials?

Gavin Watson

Other urls found in this thread:

**theshapeofmath.com**

**en.m.wikipedia.org**

**twitter.com**

Elijah Hernandez

It just werks

Carson Phillips

B-but, I just need a demonstration.

Carson Miller

>he needs to see things in order to believe them

Why don't you have faith, brother?

Jaxson Walker

chain rule

Liam Johnson

infinitesimals

Justin Wilson

y = mx

dy/dx = y/x = m

Mathfags btfo

Jordan Campbell

David Hughes

> faith

So show me the fuckin axiom that let 'em cancel out differentials, I even saw them multiply by dx/dx like if that was a 1 i mean wtf

Cooper Phillips

>dx/dx like if that was a 1

Why would dx/dx not be unity? Shouldn't it be a pretty fundamental property of differentiation?

Hudson Martinez

Because it works and it's easy to remember.

Change of variables, chain rule.

It's not an axiom, it's a set of theorems.

Usually 'dx' is used in a symbolic way, it's not a number. That's the reason it seems weird when you use it like a number (dividing), but it works because of more profound reasons.

Robert White

> it's a set of theorems.

Which ones?

> because of more profound reasons

What reasons?

Aiden Flores

chain rule

Isaac Davis

It's basically chain rule, you could read Calculus from M. Spivak for further details.

Also, remember that it doesn't work with partial derivatives: **theshapeofmath.com**

Henry Carter

>Usually 'dx' is used in a symbolic way, it's not a number.

I know, but 'dx/dx' is unity and does not require interpretation of 'dx' as a number, and is not a wrong statement. Of course you can't just cancel out 'dx'.

Leo Clark

[math] F(x, y) = 0 [/math]

[math]\displaystyle \frac{\frac{\partial{F}}{\partial{x}}}{\frac{\partial{F}}{\partial{y}}} = -\frac{dy}{dx}[/math]

This triggers the physishit

Joshua Ross

"cancelling out" differentials can be formally correct (for example in language of differential forms), so it's not like they're totally wrong. It also just werks, it's not correct the way physicists do it, but it can be treated as mnemonics for valid techniques. And we have to remember physicists are just dirty, dog eating animals and they don't do mathematics, they just try to apply the maths (but only the parts they remember and are not too hard) untill they theory works

Jeremiah Cruz

>physicists don't do mathematics

*A Physicist who won a Fields medal blocks your Path integral*

Kayden Turner

think of 3 cogwheels connected,

x, y & z

and their turning speeds

dx/dt, dy/dt and dz/dt

William Edwards

>*a mathematician who knows physics blocks your path integral*

ftfy

Robert Baker

**en.m.wikipedia.org**

>Edward Witten (/ˈwJtən/; born August 26, 1951) is an American theoretical physicis

*teleports the goalposts back*

pshh....... nothin personnel kid

Noah Rivera

This. On a Riemannian manifold [math]M[/math] the tangent space [math]T_xM[/math] at any [math]x \in M[/math] is spanned by [math]\partial_\mu[/math] whose dual basis in the cotangent space [math]T^*_xM[/math] is [math]dx^\mu[/math] such that [math]dx^\mu(\partial_\nu) = \delta_{\mu}^{\nu}[/math].

Adam Bailey

Even mathematicians use this heuristics when solving problems as it's completly useless to through the formalism when you are trying to solve a harder problem. Research doesn't has a an end of chapter list of problems.

Isaiah Murphy

Phenotype Guy as a proof that physicists know maths is just like Maria Curie being a proof that women are good at science

David Cooper

Dividing by zero doesn't trigger physicists, it just makes you look retarded.

Gavin Myers

t. Brainlet.