need help finding the angle between two vectors using maxima



Dear Jack:
Compare your commands with these:

To define vector r(t) as function of t
r(t):=[2*cos(t),3*sin(t)];

To evaluate vector v
v:r(3*%pi/4);

To evaluate vector a
a:r(3*%pi/4);

To find the angle between vector a and v
acos(v.a/(sqrt(a.a)*sqrt(v.v)));

You will obtain the answer 0 because, for this case, vectors v and a are 
the same.

I hope this help: A. Morales.