Angle Between two vectors.

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How could I create a function that will take two vectors as inputs, and outputs the angle between them in radians.

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Answer 1

Jim Riggs 2020-4-11

编辑：Jim Riggs 2020-4-11

在 MATLAB Online 中打开

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Given two vectors A and B, the dot product of the two vectors (A dot B) gives the product ABcos(ang), so to get just the angle, you want to take the dot product of two unit vectors;

Assume A = [ax, ay, az], B = [bx, by, bz]

magA = sqrt(ax^2+ay^2+az^2);  % = sqrt(A(1)^2 + A(2)^2 + A(3)^2)
magB = sqrt(bx^2+by^2+bz^2);  % = sqrt(B(1)^2 + B(2)^2 + B(3)^2)
UA = [ax/magA, ay/magA, az/magA];  % A unit vector,  = [A(1)/magA, A(2)/magA, A(3)/magA]
UB = [bx/magB, by/magB, bz/magB];  % B unit vector,  = [B(1)/magB, B(2)/magB, B(3)/magB]
cosAng = dot(UA,UB);  % = UA(1)*UB(1) + UA(2)*UB(2) + UA(3)*UB(3) 
ang = acos(cosang);  % This is the angle between vector A and Vector B, in radians

As a function;

function ang = Vangle(A,B)
    magA = sqrt(A(1)^2 + A(2)^2 + A(3)^2);
    magB = sqrt(B(1)^2 + B(2)^2 + B(3)^2);
    UA = [A(1)/magA, A(2)/magA, A(3)/magA]
    UB = [B(1)/magB, B(2)/magB, B(3)/magB]
    cosAng =  UA(1)*UB(1) + UA(2)*UB(2) + UA(3)*UB(3); 
    ang = acos(cosang); 
    return 
end