Melody

921 Questions
34316 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

+118730

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If 1/2x +1/2(1/2x + 1/2(1/2x +1/2(1/2x + ... = y,
then x = ?

This one made me think.

If you start multiplying it it out you get
1/2x + 1/4x + 1/8x ........= y

x ( 1/2 +1/4 +1/8 + .........) = y

now
1/2 + 1/4 + 1/8 + ...... is the infinite sum of a GP with a=1/2=0.5 and r = 1/2 = 0.5

limiting sum = a/(1-r) = 0.5 / (1-0.5) = 2
so
2x = y
x = y/2

Melody21 nov. 2013

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I did it on my calculator and got 1.55 * 102 ⁷ (correct to 3 sig figures)

so the leading digit is 1

is that what you meant?

Melody21 nov. 2013

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What is the slope of the line represented by the equation
-2y=x-1

Divide both sides by -2 to get y by itself
then
the slope (gradient) is the number that x is times by.

Melody21 nov. 2013

+118730

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A cone is a 3 dimensional figure. It doesn't have a perimeter.

Melody21 nov. 2013

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If x=0 what does y equal?
If x=1 what does y equal?
If x=1 what does y equal?

Now you have 3 points so you can plot them on your number plane and join them together with a long line (with arrows on the ends)

Melody21 nov. 2013

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10^x=2.99 express the solution in terms of log

log ₁₀10^x=log ₁₀2.99

x=log ₁₀2.99

Melody21 nov. 2013

+118730

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http://www.youtube.com/watch?v=zZWd56VlN7w

mean of 56.3% and a standard deviation of 8.1%. in what percent of the game will the success rate be between 50% and 60%
(I am assuming that the scores are normally distributed(

Z ₁ = (50-56.3)/8.1 = -0.77778

Z ₂ = (60-56.3)/8.1 = 0.45679

Probability that -0.7778 < Z < 0.45679

is give by the area under the normal curve and you have to read it off your z score tables. You will do one side at a time.

The you tube clip above may help you.

Melody20 nov. 2013

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use pythagoras's theorem

Melody20 nov. 2013

+118730

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sin(x)=12/9

You got an error on your calculator when you tried to do this, didn't you?

sinx = opposite / hypotenuse
What is the longest side on a right angled triangle?
what does that tell you about this fraction?

Can you work out where I am going here?

Melody20 nov. 2013

+118730

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if someone jumps off a 10.0m high tower, what will their velocity be when they reach the water?

I am going to assume no air or wind resistance and the guy falls (not jumps)
The initial height is 10, the end height is 0

Initially
y''=-g
y' = 0
y=10

ongoing
y'' = -g
y' = -gt
y = -gt ² / 2 + 10

when y=0
0 = -gt ² / 2 +10
....
t = sqrt20 / sqrtg
so
y' = -g * sqrt20 / sqrtg

y' = - sqrt(20g)

If g is approx 9.8m/s ² then y' is approx = -14

So at impact the speed will be 14m/s

Melody20 nov. 2013