### 2. Demo for MathML Codes

In this chapter, the original code is MathML. If you are using a mouse, you may show the code by right-click on a formula.

$x=−b±b2−4ac2a$

#### Cauchy's Integral Formula

$f ( a ) = 1 2 π i ∮ γ f ( z ) z − a d z$

#### Double Angle Formula for Cosines

$cos⁡(θ+φ)=cos⁡(θ)cos⁡(φ)−sin⁡(θ)sin⁡(φ)$

#### Gauss' Divergence Theorem

$∫D(∇⋅F)dV=∫∂D F⋅ndS$

#### Curl of a Vector Field

$∇→×F→=(∂Fz∂y−∂Fy∂z)i+(∂Fx∂z−∂Fz∂x)j+(∂Fy∂x−∂Fx∂y)k$

#### Standard Deviation

$σ=1N∑i=1N(xi−μ)2.$

#### Definition of Christoffel Symbols

$(∇XY)k=Xi(∇iY)k=Xi(∂Yk∂xi+ΓimkYm)$