Alan

9 Questions
9007 Answers

+17

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web2.0calc solve function working again

Those who have complained about the fact that the web2.0calc calculator has been throwing an error when solving an equation recently will be pleased to know it seems to be working properly again now (1st May 2020).

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Alan 1 mai 2020

+17

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4580

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Area of intersecting circles

Here's a puzzle for when the site activity is low!

In the diagram below there are two quarter circles of radius 1 and 2 intersecting as shown. What is the area of their intersection (i.e. the shaded region)?
lire plus ..

heureka ●●●●●●●●●●

Alan 28 oct. 2015

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A puzzle (for those who are bored!)

An equilateral triangle of side length 2 is inscribed in a circle. A rectangle, with side lengths x and y, is inscribed in another circle of the same size as the first one. lire plus ..

Brodudedoodebrodude ●●●●●●●●●●●●●

Alan 11 mai 2015

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IOM 8th year sample questions for Kes1968

Note Kes, that I won't upload any more on this site though. lire plus ..

Alan 9 mai 2015

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Extract from sample paper of the International Olympiad of Mathematics for kes198 (and anyone else who ,might be interested.

HeatherF ●●●●●●●●●

Alan 8 mai 2015

+10

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cis for Melody

Melody, the question about cis(60)^1991 + cis(-60)^1991 + 1 = 1 seems to have disappeared, so I'll answer it here for you.

cis means cos + i*sin, so using De Moivre's theorem cis(60)^1991 is the same as cis(60*1991).
If we lire plus ..

Alan 26 oct. 2014

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2603

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Obtain the first derivative of the following functions from first principles, without using a series expansion:

Obtain the first derivative of the following functions from first principles, without using a series expansion:
(i) y(x) = 3/√(2x+1)
(ii) y(x) = 4√x
Recently, I provided solutions to these first principles derivatives, but made use lire plus ..

Alan 24 juil. 2014

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the roots of 3x^2 -2x-5=0 are alpha and beta find the equation whose roots are alpha^2 and beta^2 (Posted for sacha)

So alpha = 5/3 and beta = -1
To get the (quadratic) equation whose roots are alpha2 and beta2 we construct:
(x - alpha2)*(x-beta2) = 0 or:
x2 -(alpha2+beta2)*x + alpha2*beta2 = 0 lire plus ..

Alan 22 avr. 2014

+5

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Site Graphing Calculator

I've been playing with the site calculator in its graphing mode, and I'm puzzled by the fact that I sometimes seem to get a spurious straight line through the origin on part of the graph - see example below, where I just want the e^(-x). Also, why is it highlighting lire plus ..

Alan 2 mars 2014

+33661

+1

rqwr:
find the area of regular octagon with a hyportenuse of one of the triangles made out of the vertices for 2 cm

I think this is probably what is required here:

Octagon.PNG

Alan13 mars 2014

+33661

+1

yoloswag:
]what is the square number inbetween

7-15
21-29
72-96
130-156

ty

Hint: try squaring all the integers (whole numbers) between 1 and 12 and see which ones fall in the gaps you've listed.

Alan12 mars 2014

+33661

+1

tbizzle115:
What number can be divided into 713?

The integers 23 and 31 divide 713 exactly

Alan12 mars 2014

+33661

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I like Serena:
I suspect that to the nearest hundredth was intended, which would then be 0.62.

Yes, that makes a lot more sense!

Alan11 mars 2014

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+1

j3ssvern:
a recent Harris Poll survey of 1010 U.S. adults selected at random showed that 627 consider the occupation of firefighter to have a very great prestige. Estimate the probability (to the nearest hundred) that a U.S. adult selected at random thinks the occupation of firefighter has very great prestige

The fraction of adults who think the occupation of firefighter is prestigious is 627/1010

627/1010. This is the same as the probability! However, because you mention "to the nearest hundred" I assume you want the number of adults in the population who think this. As there are roughly 300 million adults (age 18 or over) in the U.S. this means the number is

300*10^6*627/1010
This is 186 237 600 to the nearest 100.

Alan10 mars 2014

+33661

+1

vottak:
How can I solve this function and find the Maclaurin series? The function is:
f(x)=sin^2(2x).
Thank You!

Alan10 mars 2014

+33661

+1

dixonwallc:
I have a program with 144 lines in Reverse Polish Notation on an HP 35s calculator, which has only visual outputs. I would like to know if I can run a program with algebraic notation on the web2.0calc, after I convert my program to algebraic. Thank you, Dixon

The web2.0calc scientific calculator purports to be programmable - select the word "Programming" underneath it. However, I've not managed to figure out how to get this to work (if it does work!). If you look at http://hp15c.com/ there is a web-based RPN calculator there (which can also be downloaded for free).

Alan10 mars 2014

+33661

+1

Melody:
Feelsbadwhenslacks:
I need help with this question, if you can please detail how you solved it.

Problem: Find the Area of a regular octagon with side lengths 17 cm accurate to 3 decimal places.

If you are just slack I probably should not have done this for you.

I probably should have found the height to another decimal place.

140310 area of regular octagon.JPG

I think you should probably have tan(67.5) = h/8.5 Melody!

Alan10 mars 2014

+33661

+1

Mft:
What is 1/3 in decimal form

This gives you a clue:

1.0/3

In fact there are an infinite number of threes!

Alan9 mars 2014

+33661

+1

aying_mathematician:
Find the point of intersection of 5x+y=3 and 5x+2y=1

5x + 2y = 1 ...(1)
5x + y = 3 ...(2)

Subtract (2) from(1) to get

0 + y = -2 i.e. y = -2

Put this into equation (2), say,
5x - 2 = 3
so 5x = 5
so x = 1

The point of intersection is (1, -2)

Alan9 mars 2014