Calculator/Math Thread

[IanTheCuber]

Ok, I found a scientific calculator, and it is really old and works great. But some of the buttons are scratched out, and I can't figure out what their purpose is. After the calculator part is over, maybe this could be an official math thread, where you can post videos and theorems anytime you want. Any math is avaliable. So, the first button is starting for tomorrow:

To a 1, it does nothing
To a 2, it does nothing
To a 3, it goes to 6
To a 4, it goes to 24
To a 5, it goes to 120
To a 6, it goes to 720
To a 7, it goes to 5,040
To an 8, it goes to 40,320
To a 9, it goes to 362,880
To a 10, it goes to 3,628,800
To an 11, it goes to 39,916,800
To a 12, on an 8-digit calculator it overflows

[Sa967St]

Not sure whether you put this thread in "Help/Suggestions" intentionally, but it doesn't belong there.

To a 1, it does nothing
To a 2, it does nothing
To a 3, it goes to 6
To a 4, it goes to 24
To a 5, it goes to 120
To a 6, it goes to 720
To a 7, it goes to 5,040
To an 8, it goes to 40,320
To a 9, it goes to 362,880
To a 10, it goes to 3,628,800
To an 11, ti goes to 39,916,800
To a 12, on an 8-digit calculator it overflows

Spoiler:

Factorial!

[insane569]

I never use a calculator. It makes it unfair for all the other kids in class. Currently in geometry prep. Already gone through algebra 1.

[Ranzha V. Emodrach]

Ok, I found a scientific calculator, and it is really old and works great. But some of the buttons are scratched out, and I can't figure out what their purpose is. After the calculator part is over, maybe this could be an official math thread, where you can post videos and theorems anytime you want. Any math is avaliable. So, the first button is starting for tomorrow:

To a 1, it does nothing
To a 2, it does nothing
To a 3, it goes to 6
To a 4, it goes to 24
To a 5, it goes to 120
To a 6, it goes to 720
To a 7, it goes to 5,040
To an 8, it goes to 40,320
To a 9, it goes to 362,880
To a 10, it goes to 3,628,800
To an 11, ti goes to 39,916,800
To a 12, on an 8-digit calculator it overflows

Spoiler:

!

I has a TI-89 Titanium ^o^

Also, why does

equal (pi^2)/6?

[hyunchoi98]

I never use a calculator. It makes it unfair for all the other kids in class. Currently in geometry prep. Already gone through algebra 1.

But doesn't everybody else use a calculator also?
At least my middle school does.

I was so surprised when i came to the US because everybody was using calculators in class.
NOBODY was allowed to use calcs in korea.

[jeff081692]

Math is one of my majors, I honestly don't know which math is hardest but since I'm in calc 2 I will just say that.

[tozies24]

Spoiler:

!

I has a TI-89 Titanium ^o^

Also, why does

equal (pi^2)/6?

Well, one way that you can find it is that the Fourier series for x^2 is Pi^2/3 + SUM[4*((-1)^n)/n^2*cos(nx)]

There is a theorem for Fourier series that if f(x) is piecewise continuous, has period 2Pi, and one sided derivatives exist at all x in the interval, then f(x) actually equals the Fourier series. So we can express a function in terms of an infinite series which I think is cool.

Anyway, then we plug in Pi to both sides of the equation.

x^2 =Pi^2/3 + SUM[4*((-1)^n)*cos(nx)/n^2]

Pi^2 = Pi^2/3 + SUM[4*((-1)^n*cos(n*Pi)/n^2]

2*Pi^2/3 = SUM[4*((-1)^n*(-1)^n/n^2]

2*Pi^2/3 = SUM[4/n^2]

Pi^2/6 = SUM[1/n^2]

I think that there are other ways but I can't recall them off the top of my head.

EDIT: Fourier series is the process of writing a function as an infinite series. It is really applicable in engineering and physics.

[sa11297]

Math is one of my majors, I honestly don't know which math is hardest but since I'm in calc 2 I will just say that.

whats calc 2? is it like what you do after high school calc?

[Sahid Velji]

To a 1, it does nothing
To a 2, it does nothing
To a 3, it goes to 6
To a 4, it goes to 24
To a 5, it goes to 120
To a 6, it goes to 720
To a 7, it goes to 5,040
To an 8, it goes to 40,320
To a 9, it goes to 362,880
To a 10, it goes to 3,628,800
To an 11, ti goes to 39,916,800
To a 12, on an 8-digit calculator it overflows

Spoiler:

Why does it do nothing for 1 and 2? The answers should be 1 and 2 respectively.

[Noahaha]

I'm taking BC calculus, but it doesn't seem that hard. Perhaps I'm doing it wrong.

Also, it's a little odd for "themathenthusiast" to not be able to recognize factorials...