How to use the three points A1, A2, and B0 to calculate ∠A1B0A2?

[Daniel Pollard]

Do you know Pythagoras' theorem or the cosine rule?

Answer 1

[KSSV]

A1 = [171 422] ;
A2 = [415 413] ;
B0 = [277 386] ;
d1 = A1-B0 ;
d2 = A2-B0 ;
theta = atan((d2(2)-d1(2))/(d2(1)-d1(1)))

[Wesley]

After changing the other two different points, how can the calculated values be the same?

[KSSV]

Question is not clear.

[Wesley]

I'm very sorry. It was my mistake, your procedure is correct.

[James Tursa]

@KSSV: Your solution produces the angle that the A2-A1 vector makes with the x-axis. It does not involve B0 at all. This does not seem to answer the question.

Answer 2

[James Tursa]

A1 = [171 422] ;
A2 = [415 413] ;
B0 = [277 386] ;
d1 = A1-B0 ;
d2 = A2-B0 ;
theta = atan2( norm(cross([d1 0],[d2 0])), dot(d1,d2) );

See this link:

https://www.mathworks.com/matlabcentral/answers/101590-how-can-i-determine-the-angle-between-two-vectors-in-matlab?s_tid=ta_ans_results