What is the meaning of the Δi term in the equation ∑ficosΔi = 0?

[new90]

Homework Statement

question

Relevant Equations

n

∑ficosΔi = 0 what is the meaning of Δi

 

[berkeman]

Homework Statement:: question
Relevant Equations:: n

∑ficosΔi = 0 what is the meaning of Δi

This doesn't look so much like a homework problem, but more of a conceptual question?

Also, can you please show us where you got this equation? Can you maybe post a screenshot of it, or attach a picture of it? Since you did not post it in LaTeX, it's hard to interpret what it is for. Thanks.

 

[new90]

but the thing i want to know what ddoes it means Δi

 

[fresh_42]

Without context and further specification: an angle.

but the thing i want to know what ddoes it means Δi

Still an angle.

 

[new90]

ok

 

[berkeman]

I finally inserted a space in your equation before the cos() term, and got some hits. I think you are asking about this type of equation?

$$\sum{f_i}{cos(\delta i)} = 0$$

http://www.hamilton.ie/cemacs/publications/paper6.pdf

 

[haruspex]

but the thing i want to know what ddoes it means Δi

The exact format is important. Is it $\Sigma f_i\cos(\Delta i)$ or $\Sigma f_i\cos(\Delta_i)$?
What is the subject matter? What preceding references to $\Delta$ or $\Delta i$ or $\Delta_i$ in the text?

 

[Adesh]

Without context anything can be any other thing. In mathematical and physical contexts $\Delta$ generally stands for difference (usually very small one ) or a very small quantity of something. And $i$ is a dummy variable (generally).

 

[etotheipi]

Without context anything can be any other thing. In mathematical and physical contexts $\Delta$ generally stands for difference (usually very small one ) or a very small quantity of something. And $i$ is a dummy variable (generally).

I'm not sure about the 'very small' part. For infinitesimal changes we might use the little 'd'. But I see no reason why not to use $\Delta$ even if the change is very large - as far as I'm aware it's just a change, the bog standard "final - initial". We could apply a force to something, wait 10 years and measure its $\Delta E_k$.

Please do correct me if I've misinterpreted something!

 

[Adesh]

I'm not sure about the 'very small' part. For infinitesimal changes we might use the little 'd'. But I see no reason why not to use $\Delta$ even if the change is very large - as far as I'm aware it's just a change, the bog standard "final - initial".

Please do correct me if I've misinterpreted something!

You see this $\Delta$ once caused me a serious problem during my reading of Feynman Lectures on Physics, in volume 1 of FLP you will find $\Delta$ being used for small changes, however, other books tend to write $\delta$ for small changes.

 

[fresh_42]

I'm not sure about the 'very small' part. For infinitesimal changes we might use the little 'd'. But I see no reason why not to use $\Delta$ even if the change is very large - as far as I'm aware it's just a change, the bog standard "final - initial". We could apply a force to something, wait 10 years and measure its $\Delta E_k$.

Please do correct me if I've misinterpreted something!

Delta small is a very physical point of view. In other areas as mathematics or economy it is normally just any difference, often a step width.

But "i" could be anything: imaginary unit, index or variable.

 

[etotheipi]

You see this $\Delta$ once caused be a serious problem during my reading of Feynman Lectures on Physics, in volume 1 of FLP you will find $\Delta$ being used for small changes, however, other books tend to write $\delta$ for small changes.

I've just looked and you're quite right! That is awfully confusing!

I guess I'm just used to seeing $\Delta$ for a finite change, $\delta$ for a very small variation and $d$ for an infinitesimal change. But as @fresh_42 mentioned, usage amongst many different people can be very inconsistent!

 

[new90]

ok thanks