Question 921219
*[tex \large a \cdot b = 2 \times 1 + (-1) \times 3 + 2 \times (-2) = -5]


Also, *[tex \large a \cdot b = |a| |b| \cos \theta] where theta is the angle in between vectors a and b.


Find the magnitude of a and b, solve for theta and you're done.


Then use the fact that *[tex \large |a \times b| = |a||b| \sin \theta] and find *[tex \large |\sin \theta|].