 #1
 100
 0
Homework Statement
This is actually for an engineering class, but it's pretty basic vector addition.
Determine the angle θ between the two cables attached to the post.
I've attached the picture.
Homework Equations
The Attempt at a Solution
From the picture:
F_{1}:
α=?
β=?
γ= 35°
F_{2}:
α= 45°
β= 60°
γ= 120°
First, to find F_{2}, I used the angles and the formula cos(α)=(F_{2x}/F_{2})
F_{2}=<282.84,200,200>
To find F_{1}, I used the 35° from the vertical to find the z component, then used the 20° in the xy plane to find the x and y components.
F_{1}=<215.59,78.47,327.66>
F_{1}·F_{2}=F_{1}F_{2}cosθ
θ=cos^{1}(F_{1}·F_{2}/400^{2})
=cos^{1}(600.84/400^{2})=90.2°
According to the back of the book, the answer is 97.3°. So, I've made a mistake somewhere. Any help finding it would be greatly appreciated.
Attachments

27.6 KB Views: 746