Find angle in a open curve

in image step wise I show the wanted result.... But i am new in matlab in have no coding expernce so plz help me....

Answer 1

[KSSV]

Let P1, P2,P3 be three points....with P2 in middle....get two vectors and use the formula given in this link: https://in.mathworks.com/matlabcentral/answers/101590-how-can-i-determine-the-angle-between-two-vectors-in-matlab

u = P2-P1 ;
v = P2-P3 ;

[Sajid Rahim]

thank u