Belt friction - determining angles

[O011235813]

Homework Statement

A cable passes around three 2-in-radius pulleys and supports 2 blocks as shown. Pulleys C and E are locked to prevent rotatoin, and the coefficient of friction between the cable adn the pulleys are static = .20 and kinetic = .15. Determine the range of value of the weight of black A for which equilibrium is maintained (a) if pully D is locked, (b) if pully di is free to rotate.

http://img98.imageshack.us/my.php?image=circleproblemit0.jpg

Homework Equations

ln(T2/T1) = static * angle

The Attempt at a Solution

The main problem I'm having is determining the angles to be used. I can see it's a 30/60/90 triangle. So i tried using pi/3 for the D and pi/6 for C, and that didn't work.

Then i used pi/3 still for D and changed pi/6 to 2*pi/3. And that didn't work. If anyone could help me with just the angles that'd be much appreciated. I think i have everything after that down. Thanks for all the help :D

 

[O011235813]

sorry the image didn't show up ... let me try this

http://img98.imageshack.us/img98/2858/circleproblemit0.jpg
http://g.imageshack.us/img98/circleproblemit0.jpg/1/

 

[O011235813]

nvm i figured it out :D

 

[O011235813]

actually...now that I'm trying to figure out the 2nd part...i can't get it...do i have to use a couple system at D or something of that sort? use moments? or am i over thinking it? thanks once again for any help :D