Solving Mechanism Geometry Problem - A to B Rotation Degrees

[Kalus]

Ok, I have a problem similar to a slider crank but not quite.

http://imageshack.us/photo/my-images/851/sw1b.png/

Fixed points are A and B, all others are free to pivot. The beam labeled 20 is rotating around, at this snapshot 40 degrees from vertical. How can I find how many degrees back and forth the beam that is fixed at A turns in response? I'd quite like to find a general solution

I really can't figure out the geometry for this one

 

[W R-P]

this can be done with some simple construction..DRAW EVERY THING TO SCALE
Draw an arc showing the motion of the rod fixed to B.

Then divide that arc into maybe 5 pts.Measure the length the 150 rod.

From each of those 5 pts, draw an arc of radius 150(the 150 rod length).This shows the various positions of the 150 rod during the motion of the B rod.

Then from A draw an arc of radius 40(the 40 rod length) to intersect.Join the points of intersection between the various points(between the 150 rod and the 40 rod) with a curve.

I hope this is clear.

 

[Kalus]

Thank you for your reply. It is clear, however I was hoping for a mathmatical solution rather than graphical.