Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
mehr ..

Melody 02.04.2022

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Reporting problems.

There are a number of people having problems at the moment.
If you lodge an error can you please give all relevant information that you can think of.
Where you are in the world - the city or the country - is often very important information. mehr ..

Melody 16.03.2022

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How to make an empty rectangle in Latex

I just worked out how to make an empty box of various horizonal size easily in LaTex.
This is not a recommended method, but other methods that I have tried here have not worked.
This coding is really simple. Just put letters inside mehr ..

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Melody 15.03.2022

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HAPPY ANNIVERSARY CHRIS! (CPhill)

I just realized that you became a member here exactly 8 years ago today!

It has been great to have you here all that time

Off-Topic

Melody 13.03.2022

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WELCOME BACK CPHILL !

Melody 11.02.2022

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Very interesting question. No high level maths required.

This question was posted a couple of days ago.
https://web2.0calc.com/questions/geometry_73561

I think it is really interesting. It looks much more difficult than it really needs to be. mehr ..

Melody 01.02.2022

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Members have a better experience. Their questions get more attention.

Almost everyone is posting as a guest.
If you post as a member your questions will have a far greater chance of a timely and helpful response.
If you are a genuine learner and interact with us, you will become known and answerers will do mehr ..

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Melody 09.01.2022

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HAPPY BIRTHDAY CHRIS!

Melody 20.12.2021

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Some guidelines for question askers.

Please note:
1) Ask only one question per post.
2) When asking a question talk about what you have tried for yourself. Then people will take you more seriously and will be more able and willing to help.
3) If you get an answer mehr ..

Off-Topic

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Melody 04.11.2021

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Remeniscing - a little historical humour.

I just found this old post that some of you, who have been around for a while, might find amusing.

https://web2.0calc.com/questions/look-at-the-new-leader-board

Off-Topic

Melody 29.10.2021

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simplify 7a/15b^2 + b/18ab

This is the question that you have asked, is it what you intended?

simplify [ (7a/15)*b^2] + (b/18) *ab

or did you really mean

simplify 7a/(15b^2) + b/(18ab)

or maybe you meant something else ??

Melody18.11.2013

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sorry, this isn't correct.
Try to google it to find the correct answer
Also, it is the surface area of a sphere that you want.

Melody18.11.2013

+118725

0

Try working your way through a log unit
maybe
http://www.mathsisfun.com/algebra/logarithms.html

Melody18.11.2013

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How much mixture do you want to make up altogether?

Melody18.11.2013

+118725

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log(x) - (1/2)log(x+4) = 1

log(x) - log(x+4) ^1/2 = 1

log[x/(x+4) ^1/2] = 1

Now I need to know what base it is in. I will assume base 10
x/(x+4) ^1/2 = 10
etc
This will lead to a quadratic equation that you will have to solve.

You should work through a unit on logs maybe
http://www.mathsisfun.com/algebra/logarithms.html

Melody18.11.2013

+118725

0

((e^(100x)*(100sin(120pi*x)-120pi*cos(120pi*x))/(14400pi^2+10000))/e^(100x=Q What is Q?
I re-presented the question as follows - is this what the question was?

[ (e^(100x)*(100sin(120pi*x)-120pi*cos(120pi*x))/(14400pi^2+10000) ] /e^(100x)=Q What is Q?

Q = [ (e^(100x)*(100sin(120pi*x)-120pi*cos(120pi*x))/(14400pi^2+10000) ] /e^(100x)

Q = 100sin(x)- 120pi*cos(x)/(14400pi^2+10000)

Q = 1000[0.1sin(x)- [0.120pi/(14400pi^2+10000)]*cos(x)]
--------------------------------
Now using Sin(x-A)=sinx * cosA - sinA * cosx
let
cosA=0.1
sinA= 0.12pi/(14400pi^2+10000)
tanA=0.12pi/(14400pi^2+10000)/0.1 = 1.2pi/(14400pi^2+10000)
A = 2.47821*10^(-5) (to 6 sf)
-----------------------------------
Q = 1000*sin[ x - atan(1.2pi/(14400pi^2+10000))] exact if I didn't make a mistake
Q = 1000*sin[ x - 2.47821*10^(-5)] (this answer is not exact)

I think that's right but I could easily have made a mistake.

Melody18.11.2013

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11/50 * 870 Litres

It is actually
11Litres/50Km * 870km but the km cancel out. (You can cancel units just the same as you can cancel numbers)

Melody17.11.2013

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(1-sqrt(2))^2-1/(sqrt(2-1

Do you mean

(1-sqrt(2))^2- {1/(sqrt(2)} -1 ??

Melody17.11.2013

+118725

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Melody17.11.2013

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Draw the diagram
use pythagoras to ger the third side
Read the ratios off the diagram.

remmeber the word
soh cah toa
sin=o/h
cos=a/h
tan/o/a

or if you prefer, you can remember
Some old hags
Can't always hide
their old age

co t=1 / tan
co sec=1 / sin
se c=1 / cos

I am trying to show you that the
first letter of original ratio = third letter of new one.

Melody17.11.2013