член: I like Serena

1 Questions
63 Answers

754

+135

Someone should animate this!

I like Serena 31 мар. 2014 г.

+135

\displaystyle \frac or \dfrac work to make fractions bigger.

Furthermore, many sites support multiple delimiters for latex that behave slightly differently.
If you use $$\frac 1 2$$ or [ math ]\frac 1 2[ /math ] you often get bigger ("displaystyle") latex, while $\frac 1 2$ generates small ("inline") latex.

I like Serena12 февр. 2014 г.

+135

sesa:
mi fate la derivata y=log(sqrt((x^2/e^(1-x))))

Ciao sesa!

Potete vedere il derivato qui:
http://m.wolframalpha.com/input/?i=derivative+log%28sqrt%28%28x%5E2%2Fe%5E%281-x%29%29%29%29

y' = 1/x + 1/2

O volevi sapere come trovarlo?

Btw, can you also write in English?

I like Serena11 февр. 2014 г.

#30

+135

Melody:
Edit: Doesn't anyone know how people are including symbols such as integral signs and +- signs into the body of their posts?
I thought perhaps they are using the control key. Any thoughts?

You can do that by copying and pasting from about any source.
When using Windows you can use the Accessory Character Map to copy and paste them.
Pick any site where you can type latex, and you can copy and paste the symbols when viewing the result.
Pick any web page where the symbols you want are listed, e.g. wikipedia, and you can copy and paste them.

I like Serena6 февр. 2014 г.

+135

Princess Sophie E:
A ladder rests with its foot on smooth horizontal ground and its upper end against a smooth vertical wall.
The ladder is uniformed and weighs 300N and inclined to the wall at an angle x. What horizontal force must be applied to the foot of the ladder to prevent it from slipping if
a) x=30degrees
b) x=arctan(3/4)

Hey Princess Sophie E!

To keep the ladder in place, the resultant force at its bottom must be in the direction of the ladder.
The vertical force (the "normal" force) at the bottom is equal to the weight W = 300 N.
And suppose we call the horizontal force F.
Then that means that the ratio between the horizontal force F and the vertical force N must be equal to the ratio of the distance of the foot to the wall (call that d) and the height of the top (call that h).

It so happens that tan(x) is equal to the ratio of d and h.
That is:

tan(x) = d/h

So this has to be equal to the ratio of F and W.

tan(x) = d/h = F/W

Can you then find F if you know that x = 30 degrees?
And also if x=arctan(4/3)?

I like Serena5 февр. 2014 г.

+135

AngelIshtar7:
Ranges from 6.57 to 7.93. Write the desired point ± tolerance statement. How do I do this?

Hi AngelIshtar7!

As Melody said, the logical interpretation is that you need 7.25±0.68.

That is, unless those bounds are absolute upper and lower bounds, meaning it is 100% certain the measurement is in that range.
(I'm stretching here, so please clarify.)
A tolerance is intended to catch 67% of the cases.
In that case we need to make an assumption about the probability distribution.
For instance, assuming a uniform distribution, the tolerance statement would be 7.25±0.46.

I like Serena5 февр. 2014 г.

+135

Nice answer!

I like Serena5 февр. 2014 г.

+135

Melody:

e^ln(2x) = e^-4/7

2x = -4/7

Oops!
I think you dropped an "e".

Hey SelinaMarie!

I see you came up with a couple of good answers!

I like Serena4 февр. 2014 г.

+135

Girl...Just girl:
What does -7/3n= -42 equal?

I'm sorry, I just suck at algebra.

Plus it's not cheating if I tried to solve it, and I can't seem to get the answer right. I even asked my family member for help and they couldn't help me at (neither did they try to help me).

PLEASE HELP!

Hi "Girl"!

What did you try? What kind of answers have you considered?

Oh, and btw, did you mean -7/(3n) = -42, or did you mean (-7/3)n = -42?

Either way, the trick is to multiply both sides with 3 to start with.
That should make the equation simpler.

I like Serena3 февр. 2014 г.

+135

Melody:
*
Hello everybody.
I thought I would put this post here for people who would like to make comments concerning the forum.
For instance;
What things do you like.
What things don't you like.
Can you think of something that would make the forum better

Any serious comment will be appreciated.
Thank you
Melody

I like that some posters thank whoever is helping them.
I don't like so much that old threads are being bumped when there is nothing new to read.
I like that (some) younger people try to help out.
I like that Melody is taking a hand at making this forum a better place.
I especially like the end-of-day-wrap-up.

I like Serena3 февр. 2014 г.

+135

Melody:
Now, -4^2 is really tricky. Is it -4*-4 = +16? or is it - 4*4=-16 It is always best to use brackets in a situation like this so that the message is clear.
If you do it on your calculator with no brackets you will get -16 Try it and see.
The reason is that the calculator interprets it like this -4^2 = -4²= -1 * 4²

To be perfectly honest I am not sure how a person is supposed to interpret this. I will ask the other mathematicians whether they have a definite take on this.

I would interpret it as:

-4 ² = 0 - 4 ² = 0 - 16 = -16

The expression -x ² is less ambiguous, since it is easy to interpret as -(x ²).

Either way, it's best to use parentheses in cases like these.

I like Serena3 февр. 2014 г.

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