Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

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#126 Re: Help Me ! » Integral » 2009-11-06 02:10:24

Still, much appreciated smile

#127 Re: Help Me ! » Integral » 2009-11-05 17:45:28

Wow! Thanks heaps TheDude, that was amazing!
Completing the square, trig substitution, exponent reduction, trig identities...wow

#128 Re: Help Me ! » Integral » 2009-11-05 02:15:11

Thanks TheDude, but I would like do know what method was used to solve it. I've tried integration by parts but it didn't work.

#129 Help Me ! » Integral » 2009-11-04 22:49:58

Identity
Replies: 9

Can someone please show me the steps to solve:

#130 Re: This is Cool » A sum by Ramanujan » 2009-11-03 19:24:06

Thanks bobbym, I'll check it out... ramanujan was a very interesting person

#132 This is Cool » A sum by Ramanujan » 2009-11-01 03:28:38

Identity
Replies: 3

I read somewhere that Ramanujan said that

Does anyone know how this came about or where I might go to read more about it? Thanks

#134 Re: Dark Discussions at Cafe Infinity » We missed it! » 2009-10-28 23:01:30

I was having an interesting discussion about this hypothetical on another forum. What does everyone here think about it?

You must choose from one of these two options.
Option 1: You die now.
Option 2: You live until your natural time of death, but when you die the earth is destroyed with you.

#137 Help Me ! » trig substitution » 2009-10-27 19:54:06

Identity
Replies: 2

When finding

, using the substitution
we eventually arrive at

Why do we assume

is positive here? Why don't the textbooks say it's
?

#138 Re: Help Me ! » Small question.. » 2009-10-23 15:34:25

Yep, that is a fantastic theorem to remember for other problems, thanks for the derivation soroban

#139 Re: Help Me ! » how to find sin 5 degrees » 2009-10-18 02:34:27

I can't think of any way using trigonometry formulas, but complex numbers numbers could be used to derive them.

#140 Re: Exercises » Some nasty inequalities » 2009-10-17 00:41:30

Haha, unwise to use Muirhead in an IMO solution, because it is not elegant enough?
How about proving Muirhead's yourself in the exam and acting as if you didn't know it existed! That would seem like real genius.

#141 Re: Exercises » Some nasty inequalities » 2009-10-16 23:47:04

Wow, Muirhead's inequality looks quite powerful, thanks for introducing me to it

#142 Re: Maths Is Fun - Suggestions and Comments » Implicit Equation Grapher » 2009-10-12 23:56:08

Cool, thanks for fixing it

By the way,

appears to be a straight line. How can this be?

#143 Re: Maths Is Fun - Suggestions and Comments » Implicit Equation Grapher » 2009-10-09 22:40:31

I like this one a lot:

y^2*tan(x^2+y^2)=x^2-y^2

It has a ripply effect with an infinity sign in the middle

Also this one:

Also has a ripply effect, but with a yin-yang symbol

#144 Re: Maths Is Fun - Suggestions and Comments » Implicit Equation Grapher » 2009-10-09 22:37:10

I think we need more customized zooming. Rather than zooming in and out by a factor perhaps allow us to set x min-max, y min-max. Also I don't know if this is possible, but it would be nice if it could identify minima-maxima or allow us to 'trace' the graph, showing the coordinates at each point.


Also, some functions I graphed made IE stall for a very long time, for example sin(x+y/sin(x+y))=y. Perhaps you could have a 'break' button that can halt the processing.

But it's really good overall big_smile

#146 Re: Help Me ! » A Stats Equation » 2009-10-01 03:08:30

Wow this makes me realise how much I love my graphics calculator... just nSolve( and out pops the answer. big_smile
Iteration... Taylor series? eww hmm

#147 Re: Jokes » "Have I Got News For You" » 2009-09-29 16:48:27

MathsIsFun, I understand that you are busy and I'm very grateful for what you do in maintaining these forums, but do you think that next time if the first post in a thread is offensive you could just edit the post (wipe it clean) instead of deleting it?

Also Jane there's no need to get so angry over it, I'm sure MathsIsFun has given consideration to your complaints.

#148 Re: Jokes » "Have I Got News For You" » 2009-09-29 00:05:23

mathsyperson wrote:

but it's probably not a good idea to go against a moderator's decision like that.

hmm

#149 Re: Jokes » American » 2009-09-29 00:03:00

Thanks for restoring the thread Jane... seems quite uncharacteristic for a whole thread to be deleted like that...

@ bobbym:
"Personally, I can't see why it is called either. Sometimes you go down, an action not described by the name."

Nor is that described by "elevator" tongue

#150 Re: Puzzles and Games » Too tough for a homework assignment? » 2009-09-21 22:49:11

In Australia we don't learn the double angle formula in high-school (but it is a nice formula)

Although, I guess if you included the formula as a hint (and also possibly ask students to derive it), it would make the problem quite doable.

Although my solution relies on Year 12 Maths, the ending is a bit wishy-washy since it requires you to 'know' that

(which I suspect most people won't have memorized)

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