- #1
sakau2007
- 7
- 0
Homework Statement
Given the vectors:
P = 8i +5j-Pzk m
and
Q = 3i -4j-2k m
Determine the value of Pz so that the scalar product of the two vectors will be 60m2
Homework Equations
Sure seems like we will need to use the following equation:
P * Q = |P| * |Q| * cos ∅
But I don't recall being able to be taught the angle between two vectors so cos would still be unknown?
The Attempt at a Solution
Also, I assume the scalar product being 60 means that PQ = 60, or that:
Q = √32+-42+22 = √29
So, P would be 60/√29
Then this equation should be solved such as
60/√29 = √82+52+(-Pz)2
11.14172029 = √82+52+(-Pz)2
124.13793 = 89 + (-Pz)2
35.13793 = (-Pz)2
This would give an answer of about +/- 5.92, but in my solution manual I see that the solution is -28. Where have I gone wrong?