Tensions Equilibrium: Finding Unit Vectors

[allenw990]

Homework Statement

see pic

Homework Equations

The Attempt at a Solution

Ive worked out T1 which is T1=F1(-4i-5j-10k/11.8743) = T1(-0.337i-0.421j-0.842k)
and T2=F2(-4i-5j-10k/11.8743) =T2(0.337i-0.421j-0.842k)
and the next step is to find the unit vector of force M = 20kn but how do i work out unit vectors from the diagram if the lengths aren't given?

(the answer given is 6.84i + 18.794j for the unit vector of M=20kN but how??)

 

[SteamKing]

You obviously don't realize that a 'unit vector' has a magnitude = 1, which is why it's called a unit vector.

You know the magnitude of the force M (which = 20 kN) and you are shown the direction of the M vector in the diagram. The M-vector is parallel to the x-y plane and it makes an angle of 20 degrees with the positive y-axis. Ergo, you can work out the components of M using simple trigonometry.

 

[allenw990]

oh i get it now thanks