All Answers

+118741

Hi everyone,
My last wrap was 3 days ago. I was not really intending to do one tonight. The regular posts were about to 'fall off the page' and I was seriouously considering leaving them there.
Anonymous4338 made me re-think. Thank you for your post on this thread. I am glad I made you happy. You have made me happy too.

Since my last wrap many great answers have been posted by Samgelinas, CPhill, Alan, Kitty<3, reinout-g, brabrams, guest, Rom and Anonymous4338. Thank you.

Samgelinas posted an addictive web game. Thanks for that. I have added the thread address to my collective 'games' thread.

I have written a post 'Information for new members' on the 'Become a member' thread. I have talked about a few things there, I can't actually remember what - You will have to take a look.
I have however explained how the private message system works. Unless you have any particular reason not to, it would be a good idea if you set an alert pop-up for new messages.
I have explained it all in the post. I sometimes want to contact members privately. This is the only way I can do it. Other people may also want to chat.
http://web2.0calc.com/questions/become-a-member-why-would-you-want-to
I think that is it for now.
Stay happy,
Melody.

MelodyApr 4, 2014

+118741

bump

MelodyApr 4, 2014

+118741

bump

MelodyApr 4, 2014

#10

+118741

Calculator for linear regression - suggested by Alan.
http://www.alcula.com/calculators/statistics/linear-regression/

Understanding conics, focus, directric etc interactive graphing.
http://www.intmath.com/plane-analytic-geometry/4-parabola.php

MelodyApr 4, 2014

+118741

bump

MelodyApr 4, 2014

+118741

Dom:
are the lines A(3,4)B(7,7) and C(0,0)D(-6,8) parallel, perpendicular, or neather?

the formula for gradient is (y ₂-y ₁) / (x ₂-x ₁)

so the gradient of AB is (7-4) / (7-3) = 3/4
and
the gradient of CD is (8-0) / (-6-0) = 8/-6 = -4/3

Now the gradients are different so the lines cannot be parallel.
but
3/4 * -4/3 = -1
and this means that the lines are perpendicular.
If two gradients multiply to give -1 then the lines are perpendicular
And, if this is the case then one gradient is the negative reciprocal of the other one.

MelodyApr 4, 2014

+118741

Thank you all, much appreciated

I know a little more about derivatives and a little more about LaTex.
Putting this together was a real struggle.
I can't do chain rule unless I put in 100 extra steps.
This is my LONG version. (expanded from Rom's and reinout-g's - thank you)
Thanks Alan for the last bit. That was easy after all.

LaTex creates files as pdf's and I don't think I can bring pdfs into the forum. What is the best way around this?
I actually rotated this one, snipped it and then rotated it back again but it lost clarity. Also if the output was much longer it still would not have be adequate.

140404 Garage door derivative 2B.jpg

MelodyApr 4, 2014

Trey you iz nerd...So smart!

GuestApr 4, 2014

+1313

I think in part the online test allows only for the correct answer and I do not have enough knowledge to put it in correctly, in answering the question. That if I try I am not told correct parts or inccorect parts and I am given knew equations if I fail. Thus I must investigate the right answers since I could be either a little wrong or majorly wrong etc. Thanks.

StuApr 4, 2014

+1313

Thank you for the help I knew this was the right place to ask.

StuApr 4, 2014

#90

+1667

I just found out about this! When I realized that my name was on here 4 times, I was really happy.
I'm glad you are thanking people for their efforts.
I haven't been able to check the forum the last month, but I'll probably be a little more busy now!
Or maybe not. I moving in a week. Anyway, thanks agin, Melody!

Anonymous4338Apr 4, 2014

+118741

Anonymous4338:
RETURN OF ANONYMOUS 4338!
Bet you people didn't expect me to come back!
I got fish by putting a reverse 2 next 2 a regular 2.

A strange looking fish but okay

i am glad that you are back

MelodyApr 4, 2014

389840139101 is the answer

GuestApr 4, 2014

+1667

An 8 foot tall baby giraffe's shadow is 4 feet, which is half of 8 feet. That means a shadow of something would be 1/2 of an object's actual height. If the globe's shadow is 1 foot long, which is half of the globe's actual height, you would multiply the globe's shadow by 2. The globe is 2 feet tall.

Anonymous4338Apr 4, 2014

+1667

RETURN OF ANONYMOUS 4338!
Bet you people didn't expect me to come back!
I got fish by putting a reverse 2 next 2 a regular 2.

Anonymous4338Apr 4, 2014

+118741

Guest:
How do I solve cosB=.375?

Hi,
when you are looking for an angle you have to use inverse cos or arc cos.
These are different names for the same thing.
the notation is
cos ^-10.375
or
acos0.375

acos(0.375)

With most calculators you will need to press the 2nd function key to get access to cos ^-1 and you don't always need the brackets
Make sure your calc is set to degrees. There will probably be a tiny D at the top of the screen.
so you would press

2nd Cos ^-1 0.375 =

MelodyApr 4, 2014

Apr 3, 2014

+118741

JamesJonez:
I have a 25% chance to succesfully finish a task. What is the chance of it failing 9 times in a row?

The chance of failing once is 75% = 0.75

the chance of failing 9 times in a row is (0.75) ⁹

MelodyApr 3, 2014

It is 18

GuestApr 3, 2014

+118741

ERS:
least common multiple of 9and 6

the multiples of 9 are 9, 18, 27, 36, 45, 54,.....

The multiples of 6 are 6, 12, 18, 24, 30, 36, 42, 48,........

The least common multiple is the smallest number that is in both lists.

MelodyApr 3, 2014

+2355

Dic:
Ask a Math Question!
Formula to convert engine RPM in to MPH in different gears?

Since I'm no car expert I don't know the exact formulas which would lead from one to another (simply because I don't know all the in-between steps between gear rotation and wheel rotation)

I could give you the general formula to calculate the speed of a wheel rolling when you know the RPM and the diameter, but I guess that wouldn't be much help either.

I found this online; http://www.bgsoflex.com/rpmmph.html, which, if you can find out how to calculate each term, might help you.

Hope that will work

Reinout

reinout-gApr 3, 2014

+118741

Hi Mic,
You could take a look at this thread. It may well be useful to you.

http://web2.0calc.com/questions/negative-exponents-negative-indices

MelodyApr 3, 2014

+2355

Dom:
are the lines (3,4)-(7,7)AB and (0,0)-(-6,8) parallel, perpendicular, or neather?

Let's first draw them on graph paper;

Knipsel20.PNG

We can see that they are obviously not parallel, but they can be perpendicular.

Let check what the gradients of both lines are,

for the first line, if x increases with 4, y increases with 3, so if x increases with 1 y increases with 3/4.

for the second line, if x increases with 3, y decreases with 4, so if x increases with 1 y decreases with 4/3.

So the gradient of line 1 is 3/4 and the gradient of line 2 is -4/3

The rule is that if line B is perpendicular to line A, then gradient(B) = -1/gradient(A) and similarly gradient(A) = -1/gradient(B)

Why? It's a little much to explain but you can find the full explanation here; http://www.mathsisfun.com/algebra/line-parallel-perpendicular.html

Since -1/(3/4) = -4/3 and -1/-(4/3) = 3/4 the lines are perpendicular.

Reinout

reinout-gApr 3, 2014

+33669

mic:
What is equivalent to 50(1/2)^t-2/5

Do you mean 50(1/2) ^t - 2/5? In which case it can be written as 50/2 ^t - 2/5 or 50*2 ^-t - 2/5, for example.

Or did you mean 50(1/2) ^t-2/5? In which case it can be simplified to 10/2 ^t-2 or 10*2 ^2-t, for example.

Or did you mean something else entirely?

AlanApr 3, 2014

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