mathematical riddle

[daofeishi]

Keeping in line with my vow to try and maximize my exposure to Chinese every day, I was searching for some online textbooks on a certain field of math that I am taking a class on. For some reason I couldn't find the information I was looking for, and I got really frustrated until I realized that Google Pinyin was returning the wrong characters for the second half of the word. I posted my mistake on Facebook, and it didn't take long before one of my friends responded with the following picture. I thought it was too funny not to share. You might need some mathematical background to get it, but if there is a place online where this riddle will be understood, it has to be here.

I guess the riddle is, what mistake did I make and what was I actually looking for? ;)

[gato]

You transposed the characters? ;-). Google wasn't able to suggest the right word?

[daofeishi]

Heheh, no, that's not quite it. It's supposed to represent a certain field of math ;)

[gato]

I mean let x, y be two Chinese characters, did you wrote "yx" instead "xy"? If you did, then I will know my guess for the area of math is correct.

[roddy]

Something about

袋鼠/代数

but that's as far as I can get.

[daofeishi]

@gato: nope, that's not the mistake I made. Roddy has half of it (as I'm sure you did too). The first half might require some familiarity with that field of math.

[James Johnston]

Does the second half (the shape of the equation) have something to do with cross-multiplication?

[Archie.]

I know an equation in 袋鼠：

f(f'(x))=f'(f(x)) =x

（They are equal providing x in the area where both f(x),f'(x) have legal definition）

f'(x) is the inverse function of f(x), it is usually noted as f-1(x), but I note it as f'(x) instead.

[SiMaKe]

My lame guess is 交换代数 (you typed 交换袋鼠）which would match the image fairly well and be consistent with all the clues you gave. But if you are a little less advanced 线性代数 might work but is a stretch, as is 李代数.

Or I could be missing the whole riddle. This is the most likely option.:rolleyes:

[Edit] 交换代数 is commutative algebra (where a*b=b*a). See WP if interested. BTW, this field (no pun intended) is basic to algebraic number theory (and others) which in turn has applications to cryptography/encryption technology.

线性代数 is linear algebra.

李代数 is Lie algebra.

[Xuesheng123]

The fundamental theorem of calculus?

[daofeishi]

Spot on, SiMaKe. The answer is 交换代数. The drawing shows what commutative kangaroos would look like :rolleyes:

Probably a bit of a stretch this one, but since I've been doing math for quite some years now I was amused.

[SiMaKe]

@daofeishi

Actually I thought it was quite clever of your friends.

Say hello to Atiyah and MacDonald for me if you run into them. :-)

[gato]

Oh, I thought I learned all I needed to learn about commutation back in high school.

[SiMaKe]

@gato

But you should know there is always more to associate with the distribution of knowledge.

And that you need to differentiate those ideals to integrate them into the manifold dimensions of your life.