Math  Vectors
posted by Autumn .
Relative to an origin O, the position vectors of points A and B are given by
OA = 3pi + 4j + p^2k, and
OB = pi + 1j + p^2k
Find the values of p for which angle AOB is 90°
So here's my work so far:
If angle = 90° then OA.OB = 0
OA.OB = p^4  3p^2  4
p^4  3p^2  4 = 0
Let x = p^2
x^2  3x  4 = 0
x = 4 or 1
What do I do now?
Thanks for the help!

Math  Vectors 
Reiny
remember you let y = p^2
so p^2 = 4 > p = ± 2
or
p^2 = 1 , which has no real solution.
so p = ± 2 
Math  Vectors 
Autumn
Wait, but doesn't the question say 'values'?

Math  Vectors 
Autumn
Oh wait, just realized how dumb that was! Had a brain fart, thanks for clearing things up!
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