# Draft

## 2 Android

H2O APN setting

• Name: ATT Nextgenphone
• APN: att.mvno
• Port: 80
• MMSC: http://mmsc.mobile.att.net
• MMS Proxy: 66.209.11.33
• MMS Port: 80
• MCC: 310
• MNC: 410
• APN Type: default, mms, supl, fota, hipri
• APN Protocol: IPv4/IPv6

Unset but with value:

• MVNO Type: None
• Bearer: Unspecified

Everything else Not set, including

• Proxy
• Username
• Password
• Server
• Authentication Type
• MVNO Value

## 3 C

### 3.1 Context Sensitivity of C

Here is the C lexer rule and grammar for yacc

## 4 Math

### 4.1 Calculus

Calculus has two main branches:

• differential calculus
• it is mainly about derivative. The process of finding a derivative is called differentiation.
• $$\frac{dy}{dx}|_{a}$$ is Leibniz's notation
• f'(a) is Lagrange's notation
• integral calculus
• definite integral
• indefinite integral (also antiderivative)

### 4.2 Lagrange multiplier

When solving a maxima of a function, with subject to a constraint, we often use Lagrange multiplier. Say:

• maximize $$f(x,y)$$
• subject to $$g(x,y)=0$$

We are going to introduce the Lagrange multiplier $$\lambda$$ such that

• $$L(x,y,\lambda) = f(x,y) - \lambda g(x,y)$$ is called Lagrange function.
• Compute the gradient of L, and compute the stationary points. Those points will be the space of the solution to the original maxima problem.

The intuition: at a maximum, f(x,y) cannot be increasing in the direction of any neighboring point where g = 0.