To know what kind of culture America has in High School Math, teaching a typical class in first year university or Community College will give you a very good idea.  The image below is only funny here, never funny or brought up in Singapore.

so what other kinds of funny errors do they have a lot (and laugh it off)?  Here is another off my colleague’s door.  There are so many of these, someone publish it into a book.

Door Joke of a US college Mathematician

So when you teach the students, they really got all confused in their algebra.  Off the top of my head, here is a list of what’s considered common in the US:

• $0!=0,\ln(1) = 1, \cos(0)=0, e^0= 0$
• $(x+y)^2 = x^2+y^2, \sqrt{A+B} = \sqrt{A}+\sqrt{B}$
• $(x+y)^2 = x^2+y^2, \sqrt{A+B} = \sqrt{A}+\sqrt{B}$
• $\int \frac{1}{1+\cos^2 x} = \ln(1+\cos^2x), \int \tan x = \sec^2 x$
• $\frac{d}{dx} a^x = x a ^{x-1}$
• $\int \frac{1}{x^2+x} = ln|x^2+x|+C$
• $\frac{\sin x}{n} = si x, \frac{\sin x}{x} = sin$
• $2^x = y \Rightarrow x = \frac{y}{2}$

But like an Olympic swim clinic, my job here is to correct a future Olympian’s error or bad habit.  And different students have different bad habits.  So this is like a Dharma Master trying to help his student with his affliction.  With constant diligence, the student will hope to let go and reduce his kleshas.

Let me end with another so-called funny Math joke.  If you are a Singaporean who commit this error and your parents saw it, it will hardly be funny