Need help creating array for a large data set

Hi, im a few hours new to matlab, and have a pretty urgent question

How do i create an array of angles between 2 lines from an array of x-y points? i understand how to do it if i want to calculate of 3 points, but i have almost 1000 points to handle, and i can't simply define each line segment individually.

for an array A with 2 columns where first column denotes x axis and second denotes y axis, and A[1,1]= first point i figured i'll need to do something similar to define length

P_ij = sqrt[(A[i,1]-A[j,1])^2+(A[i,2]-A[j,2])^2]

to get an array of a two columns of where first column: j=i+1, second column: j=i+2.

but i dont know the commands to input the indices i&j and how to construct this array with the conditions needed.

from there as i need to determine the angle between each subsequent segment, i figured i would need to define

theta_k=Acos[(2P_k,k+1 P_k+1,k+2)^-1 *(P_k,k+2^2-P_k,k+1^2-P_k+1,k+2^2)]

but again, i don't know if i can even denote the k+2 k+1 elements properly to create this new single column array for the angles :/

i'm sorry if i'm being problematic, been watching alot of tutorials and searching through the internet but can't find anyway in which i can do this