A vector A of R^3 has modulus 2 and forms with vectors i and j angles of 60° and 120° respectively. Determine vector A
If A = ai+bj+ck then its direction cosines are
a/2 = cos60°
b/2 = cos120°
c/2 = cosθ (where θ is not yet specified)
A = i-j+ck
since |A|=2, it looks like c=0, so
A = i-j
actually, I misspoke. The direction cosines squared sum to 1.
A can be anywhere on a circle of radius 2, which makes the desired angles with the i- and j-axes.