Anyone able to help with these vectors geometry and planes questions?

[Carlito]

Can anyone help me with parts (b) and (c) of this question: http://203.219.144.182/carl/q1ii.gif


I've done parts (i) and (ii) but can anyone help with parts (iii) and (iv)
http://203.219.144.182/carl/q2.gif

answers for parts (i) and (ii):
http://203.219.144.182/carl/q2a.jpg


Thanks heaps, it is really important and kinda urgent.

[arildno]

b) You should use the cosine-formula to express thess these lengths.
Also, remember the relation between the inner product, vector lengths, and the cosine of the angle between the two vectors.
c) Ought to follow easily from b)