Convex optimization

The optimization problem have two components that are objective function $f_0:R^n\to R$ and the constraints. The objective function and constraints keep in check each other and make balance at saddle point i.e. optimal point. The dual (Lagrange) problem of the optimal problem also solve the optimization problem by making low boundary. The dual problem can be explained as a conjugate function $f^{\ast }=sup(x^{T}y-f(x\left)\right)$.

The purpose of approximation is finding optimal point $x^{\ast }$ i.e. $\nabla F\left(x^{\ast }\right)=0$. We need a step/search direction $\Delta x$ and step size $t$. Taylor approximation has polynomial arguments that is a step and parameters of derivatives at the start point. The first degree of Taylor approximation has one adding term from start point $(x_0,F(x_0\left)\right)$. The adding term $\nabla F\left(x\right)\Delta x$ is consistent with a parameter (gradient $\nabla F\left(x\right)$) and a argument (step $\Delta x$).