# Trouble understanding L1 and L2 cost function [duplicate]

When reading the Sklearn User Guide, one might see the following statement about Logistic Regression

As an optimization problem, binary class L2 penalized logistic regression minimizes the following cost function:

Similarly, L1 regularized logistic regression solves the following optimization problem

I do not understand what the first part (before the + C) on the first equation means. I understand that w is a vector and wt is the transposition (I think). Why is it multiplicated by 1/2 ?