Posted by **Anonymous** on Saturday, March 29, 2008 at 4:29pm.

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.

- Math -
**Damon**, Saturday, March 29, 2008 at 4:33pm
a + b = (3-2) 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 :)

- Math -
**Damon**, Saturday, March 29, 2008 at 4:37pm
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 = (3-0)i + (4-0) j + (5-0) k

and

|OD| = sqrt (3^2 + 4^2 + 5^2)

=sqrt (9 + 16 + 25)

= sqrt(50)

= 5 sqrt(2)

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