Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
lire plus ..

Melody 2 avr. 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. lire plus ..

Melody 16 mars 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 lire plus ..

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Melody 15 mars 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

Hors sujet

Melody 13 mars 2022

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WELCOME BACK CPHILL !

Melody 11 févr. 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. lire plus ..

Melody 1 févr. 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 lire plus ..

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Melody 9 janv. 2022

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HAPPY BIRTHDAY CHRIS!

Melody 20 déc. 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 lire plus ..

Hors sujet

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Melody 4 nov. 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

Hors sujet

Melody 29 oct. 2021

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Yes sure,why not.

Melody2 oct. 2013

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25.28 is rational so long as it has not been rounded off. (If it was rounded off it may be an approximation for an irrational number)
cm^2 has nothing to do with it.

Any number that can be expressed exactly as a fraction can also be expressed exactly as a terminating or recurring decimal, and, all these numbers are rational.

Melody2 oct. 2013

+118725

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Ok I got it, your a stands for arc and arcsin means inverse sin.

Solving it is easy
tan(asin(1/3) )
let alpha = arc sin (1/3)
so 1/3=sine alpha

Draw a right angled triangle
let alpha be one of the acute angles
sine alpha = 1/3 so put the 1 on the opposite side and 3 on the hypotenuse
Use pythagoras to get the other side
Now you can read the tan value straight off the triangle

Tan(arcsin(1/3)) = 1/(square root of 8) = (root2)/4

Melody2 oct. 2013

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Your question does not make sense to me, Do you mean
tan(inv sin 1/3) ?

Melody2 oct. 2013

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Melody2 oct. 2013

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Don't you have a calculator? anyway it is 1 and 1/5

Melody2 oct. 2013

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No because it is only 1 dimensional

Melody2 oct. 2013

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1875/10000 but then you can simplify

Melody2 oct. 2013

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The width of a hydrogen atom is 5 × 10–8 mm (millimeters). If the moon is 3.7 × 106 km (kilometers) from Earth, how many times the width of a hydrogen atom is the distance from the earth to the moon?

I have taken the liberty of rewording your question. Is this what you meant?

The width of a hydrogen atom is 5 × 10^(–80 mm (millimeters). If the moon is 3.7 × 106 km (kilometers) from Earth, how many hydrogen atoms will fit in a row between the earth and the moon.

i don't know about hydrogen atoms but the distance to the moon is closer to 384400km which is much further than 3.7*106.

Anyway

3.7 x 106km = 3.7 x 106 x 1000 x 1000 mm = 392.2 x 1000000 mm = 3.922 x 10^8

3.922 x 10^8 / 5 x 10^(-8) = 7.844 x 10^15

Melody2 oct. 2013

+118725

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9.0

I guess that's what you want.

Melody2 oct. 2013