MATLAB: Doesn’t atan2 (u,v) give me the right angle of two simple vectors

MATLABvectorvectors

Hi All
I was using the atan2(u,v) to calculate the angles between vectors, untill I checked it for
u=[0,0,0] 
v= [1,1,1]
doing : 
teta=atan2(norm(cross(u,v)),dot(u,v));
I get teta = 0
I am expecting teta = 54 °
where am I going wrong ?

Best Answer

Of course this code replies 0. If one of the vectors is the Null vector, there cannot be an angle different from 0.
So the only problem is that you expect 54°. atan2 will not reply degrees at all, but radians.
u = [1, 0, 0]
v = [cos(0.123), -sin(0.123), 0]
atan2(norm(cross(u,v)),dot(u,v))
>> 0.1230   % As expected
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