- #1

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## Homework Statement

Im given vectors:

b = x hat + y hat

c = x hat + z hat

## Homework Equations

http://imgur.com/a/iHTOT

## The Attempt at a Solution

so I have 2 eq's... one says:

r * s = rscos(theta)

the other is a summation saying multiply x component 1 with x component 2, add y component 1 with y component 2, and so on.

Ok so I start with method 2: 1*1 x hat + 1* 0 y hat + 0*1 z hat

so you end with 1 (my books answer).

But when I use "r * s = rscos(theta)" I find the angle between them is 90 degrees so I get 0.

Whv does 1 formula work in this case but the other doesnt