Question

Let a, b, c, d be 4 unit vectors such that each is inclined at angle x with the other.

then cos x=
(a) 1/2
(b) -1/2
(c) 1/3
(d) -1/3

Answer 1

please help

Answer 2

must be d) -1/3..i m not very sure...the angle is 109.5 degree..

Answer 3

How did u get that ?

Answer 4

If the vectors are in a plane the angle is a right angle

Answer 5

But I don't know if they are in a plane or not

Answer 6

i guess they cannot be in a plane because cosine of nighty degrees is zero which isn't an option

Answer 7

buddy @UnkleRhaukus : they cant be in a plane as all vectors are not making 90 with each other.they are only making 90 with their neighbours in the fig...

Answer 8

yes

Answer 9

what dhould be the answer