Static equilibrium force decomposition problem

[Navyeel]

Homework Statement

I dont fully understand why the decompositions of forces.

Relevant Equations

F stands for friction, N is normalforce.

If you see the $\sum \tau_0 = L\cdot N_1 \cdot cos \theta - LF_1 sin \theta - L/2 \cdot G cos \theta$, all the trigonemetric parts are all opposite of what i can understand, given the angle as drawed in the Picture/url.

Please help me :)https://pasteboard.co/IiXr8qA.png

 

[Navyeel]

I think I got it, my fault was that i forgot that in torque that if i use perpendicular radius i will get the cosines and the sinus parts correct :)

 

[CWatters]

Yes it's always the perpendicular radius you need to use.

I note they are summing the torque about an axis at the top of the ladder.

 

[jbriggs444]

If you see the $\sum \tau_0 = L\cdot N_1 \cdot cos \theta - LF_1 sin \theta - L/2 \cdot G cos \theta$

To get that LaTeX to render, you need doubled dollar signs like so:
$$\sum \tau_0 = L\cdot N_1 \cdot cos \theta - LF_1 sin \theta - L/2 \cdot G cos \theta$$

 

[Navyeel]

Ah ok, thanks