Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
read more ..

Melody Apr 2, 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. read more ..

Melody Mar 16, 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 read more ..

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Melody Mar 15, 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 Mar 13, 2022

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WELCOME BACK CPHILL !

Melody Feb 11, 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. read more ..

Melody Feb 1, 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 read more ..

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Melody Jan 9, 2022

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HAPPY BIRTHDAY CHRIS!

Melody Dec 20, 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 read more ..

off-topic

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Melody Nov 4, 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 Oct 29, 2021

+118725

0

10000 * 0.1287128712871287..=1287.128712871287

1* 0.1287128712871287 = 0.1287128712871287

(10000-1) * 0.1287128712871287 = 1287.12871287 - 0.128712871287...

9999 * 0.1287128712871287 = 1287

0.1287128712871287 = 1287 / 9999

you can now cancel down to get the most simple fraction possible.

MelodyNov 11, 2013

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You have to divide it by 8

The first on is 3/8 of total
THe second is 5/8 of total

MelodyNov 11, 2013

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0

100 is the better answer.

MelodyNov 10, 2013

+118725

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I think that this is in the North Atlantic ocean, near Nova scotia, Canada.
I don't know anything about the climate except that it would be too cold for me!

MelodyNov 10, 2013

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0

What is the number of nautical miles between place A (15°N, 90°W) and place B (40°S, 90°E)?
The answer should consist relative to [ 9600 n mi]

I was thinking......
These 2 places are on a great circle of the earth. (90degreesW and 90degreesE are 180degrees apart.)
This means that the shortest distance between them is via the north or south pole.
40degrees South is further from the equator than 15degrees north so i am going to go via the south pole.
The south pole is 90degrees south

40degrees to 90degrees is 50degrees so B is 50degrees worth of distance from the south p ole
Going up the other side now.
The south pole to the equator is 90degrees.
The equator to A is 15degrees

50+90+15 = 155 degrees. (This is less than half of 360 degrees so it must be the shortest way)
Now 1 degree at the centre of the earth is 60nm at the equator (which is another great circle)
so
155 degrees * 60 = 9300nm

MelodyNov 8, 2013

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http://www.movable-type.co.uk/scripts/latlong.html

I haven't worked it out yet but this site may help you.

It works it out in km which seems a bit odd but you can do the conversion.
1 nautical mile (nm) = 1.85200 kilometer (km).

Maybe you already know that 1 degree of arc from the centre of the Earth is equal to 1 nm at the equator.

There might be a much better way of working it out. I really don't know.

You can ignore this stuff, I have answered again below.

*

MelodyNov 8, 2013

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0

if P=(2^a)(b), f(P)=2^-a,
then find f(n^3-2n^2+n) for n=even and positive integer.

This is an odd question but here goes.

P=2 ^ab ==> 2 ^a = P/b ==> 2 ^-a = b/P (P<>0 and b<>0)
So
f(P) = 2 ^-a = b/P

f(n ³-2n ²+n)

= b/ ( n ³-2n ²+n )

= b / [n(n-1) ²] where n<> 0 or 1

This is fine since n = an even and positive integer.

I think it is finished now.

MelodyNov 8, 2013

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Is the square root of seven over nineteen a rational number or irrational number? Explain

It is irrational.

An irrational number is one that cannot be expressed exactly as a fraction.
This means that it also cannot be expressed as a terminating decimal or as a recuring decimal.
When your calculator gives you an answer, it is really giving you an estimate.

seven and nineteen are both prime numbers so you can't cancel the fraction down
and 7 and 19 do not have exact square roots so
root7 and root19 are both irrational numbers
so root(7/19) must also be irrational.

MelodyNov 7, 2013

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Thanks MrBigbig.
I don't know why I didn't think of that.

MelodyNov 7, 2013

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my sister draws two similar triangles in the sand. the larger triangle has side lengths of 12,16 and 20 cm. what are the dimensions of the smaller similar triangle.

could be 6 8 and 10
or
3 4 5
or many other lengths so long as all the 12,16 and 20 are all divided by the same number.

MelodyNov 7, 2013