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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what is the slope-intercept form of (9,65) and (10,52)

gradient (slope) = (52-65) / (10-9) = -13/1 = -13

remember, it is rise on run
it is the y axis that rises
and the x axis that run

MelodyNov 14, 2013

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What is the value of the expression −3x2y + 4x when x = −4 and y = 2?

do you mean −3*2y + 4x when x = −4 and y = 2?

Just substitute in the numbers but remember there is a * sign between 2 and y, and between 4 and x

MelodyNov 14, 2013

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I answered this question for someone else recently - yesterday I think.

MelodyNov 14, 2013

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0.012 = 0.012*100 % = 1.2%

MelodyNov 14, 2013

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how do you do the problem log base 3 of 20 -log base 3 of 6 - log base 3 of 30

=log base 3 of (20/6 divided by 30)

=log base 3 of (20/6 * 1/30)

=log base 3 of (1/9)

=log base 3 of (3 ^-2)

=-2 log base 3 of 3

= -2 *1
= -2

I suggest that you work through this web site
http://www.mathsisfun.com/algebra/logarithms.html

MelodyNov 14, 2013

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MelodyNov 14, 2013

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3x {(2x-y over 3) - (x-2y over 6)}

Do you mean 3x { [ 2x - (y/3)] - [x - (2y/6) ] } ?

= 3x { [ 2x - (y/3)] - 1 [x - (2y/6) ] } (remember that there is an invisible 1 )

= 3x { 2x - y/3 - x + 2y/6 }

=(3x/6) ( 12x - 2y - 6x + 2y )

=x/2 ( 6x )

= 3x ²

MelodyNov 14, 2013

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i = sqrt (-1)
It is an 'imaginary number'
University mathematics often involves imaginary numbers.
i is the most basic imaginary number that there is.

so
At school, the sqrt(-9) does not exist because you can't find the square root of a negative number.
if you study mathematics for long enough you will learn that

sqrt(-9) = sqrt (9*-1) = sqrt9 * sqrt(-1) = 3i

Sometimes maths gets a bit magical.

You might find this web page interesting
http://www.mathsisfun.com/numbers/imaginary-numbers.html

MelodyNov 14, 2013

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1/20 * 1/19 * 1/18 * 1/17 * 1/16

MelodyNov 14, 2013

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A 20 centimeter pendulum swings in front of a metric ruler. The bob(Weight on the end of the pendulum) is releases from a position of 36 centimeters. It swings to the 14 centimeter positionbefore winging back to 36 centimeters.
What is the period of the pendulum?=
2pi sqrt(20cm/(980(cm/s^2)))= 9 sec.

To tell you the truth I don't even understand most of this question eg where is the 36cm and 14 cm measured from?

Anyway, I googled it and came up with this web page
http://www.algebra.com/algebra/homework/Rational-functions/Rational-functions.faq.question.66609.html

It says that T=2pi[sqrt( l/g )]
where l is the length of the pendulum so l = 20cm
and g = gravity = 9.8m/s 2 = 980cm/s ²
So
T = 2pi[sqrt (20/980)]
T = 2pi (1/7)
T = 0.897 seconds approx
T = 0.9 sec approx

Since I don't understand your question I really couldn't say if this is correct.

MelodyNov 14, 2013