Why doesn't atan2 (u,v) give me the right angle of two simple vectors?

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 ?

[KSSV]

Why do you expect it to be 54? IT is showing correct.

teta=atan2d(norm(cross(u,v)),dot(u,v));

Answer 1

[Jan]

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

[Steven Lord]

FYI if you want degrees you can use the atan2d function.