Math
posted by Anonymous .
If a = 3i + 2j  k and b = 2i + j calculate each magnitude.
a) a + b
I got sqrt3, but the answer at the back of the book says sqrt11.
2) If D(3,4,5) and E(2,1,5) are points in space calculate each expression and state what it represents.
OD
can you please do those and explain steps.

a + b = (32) i +(2+1) j +(1+0) k
= 1 i + 3 j 1 k
sqrt (1^1 + 3^2 + (1)^2 )
sqrt ( 1 + 9 + 1)
sqrt (11)
The book wins again :) 
Wow I accidentally put a  in front of 2 and ended up with 1. Thanks!

2) If D(3,4,5) and E(2,1,5) are points in space calculate each expression and state what it represents.
OD

I assume 0 is the origin (0,0,0)
so OD = (30)i + (40) j + (50) k
and
OD = sqrt (3^2 + 4^2 + 5^2)
=sqrt (9 + 16 + 25)
= sqrt(50)
= 5 sqrt(2)