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

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l2-xl>4

I think that these are easier to understand if you draw a rough number line.
0 is in the midle of your number line and you will need to mark 4 and -4 on it.
Now absolut value meant the distance from 0 on the number line.
So, the distance from 0 on the number line is more than 4.
Colour the bits on the number line that are more than 4 units away from 0.

Hopefully you have marked
2 - x < -4 and 2 - x > 4

Now, can you solve these 2 equations, get 2 answers?
It might then be finished or you might have to think a little more.

MelodyNov 4, 2013

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0=tan-1(ytot/xtot)=tan -1(22km/39km)

Sorry Jamie,
Your question does not make sense.

tan of what?
What is ytot and xtot?

MelodyNov 4, 2013

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Start by multiplying both sides by 3
Then expand the brackes and collect like terms for each side seperately.

Does that at least get you started?

MelodyNov 4, 2013

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If O is 4, F is 3, and X is 1900, what does the FOX say?

What a cute question.

3*4*1900 = 22800

The fox says 22800 (at least thats what crazy mathematicians think.)

MelodyNov 4, 2013

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You can not find the square root of a negative number. There is no answer.
(not in the real world anyway)

MelodyNov 4, 2013

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Hi TG,
This is an interesting little question!

"At 7 am Brooke leaves home to go on a business trip driving 35 miles per hour. Fifteen minutes later, Bart discovers that Brooke forgot her presentation materials. He drives 50 miles per hour to catch up with her. If Bart is delayed 30 minutes with a flat tire, when will he catch up with Brooke"

Let the distance travelled by X. This is the same for both of them.
Let T= time that Brooke travels (in hours)

Your first question is:
If Brooke travels for T hours, how long does Bart travel for (in hours)?

You have to set up an equation for Brooke and another equation for Bart

Use speed=distance/time, except you will want distance to be the subjsect of both fromulas

Now solve them simultaneously to find T

Is that enough help?

MelodyNov 4, 2013

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Translation

How to convert large number in small one to two digit
How to convert a huge number in the equivalent of one or two digits?

Can you give a example of what you want to do ?
Make sure there are numbers in your example.

Pode dar um exemplo do que você quer fazer?
Certifique-se que existem números no seu exemplo.

MelodyNov 3, 2013

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X/3-1/2=x/5+ 3/2

The lowest common denominator is 2*3*5 = 30
multiply both sides by 30 (use brackets)
That will get rid of all the fractions and then hopefully you will be able to do it yourself.

MelodyNov 3, 2013

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Solve 2(Sec x)^2=5tanx-1

I tried the usual method and it didn't work for me so I decided to get a bit inventive.

I said, let t=tanx
now you can draw a right angled triangle and let x be one of the acute angles.
let 't' be the opposite side and 1 be the adjacent side.
Now you have a triangle where tanx = t
Use pythagoras to get the hypotenuse = Sqr(1+t^2)

So now sec x = [ Sqr(1+t^2) ] / 1

2sec^2 x = 2(1+t^2)
So
2(1+t^2) = 5t - 1
rearrange and factorise and you get
(2t-3)(t-1) = 0
so t = 3/2 or t = 1
t=tanx

If t=1 then x = pi/4 +- n*pi Where n is an integer

If t=3/2 then x = atan(3/2) +- n*pi

Hence
x = pi/4 +- n*pi OR x = atan(3/2) +- n*pi Where n is an integer (atan stands for arc tan which is the same as inverse tan)

I did consider this a little more, sometimes 1 or more of answers gained like this can be wrong because of negative signs (you do need to be careful) but
2(Sec x)^2 +1 is always going to be positive so x needs to be in the 1st or 3rd quadrant so I don't think there is any need to be concerned.

MelodyNov 3, 2013

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Solve 2Sec^2=5tanx-1
I assume you meant

Solve 2(Sec x)^2=5tanx-1

It's got me stumped too for the moment. But I am still playing with it.

MelodyNov 3, 2013