Finding the Third Force to Achieve Zero Total Torque on an Equilateral Triangle

[merced]

http://img300.imageshack.us/img300/4792/physics1gj9.th.png

"Two forces $$F_1$$ and $$F_2$$ act along the two sides of an equilateral triangle as shown...Point O is the intersection of the altitudes of the triangle. Find a third force $$F_3$$ to be applied at B and along BC that will make the total torque zero about the point O."

So the sum of the torques = 0. I don't know what to do first. Should I put the forces into component form and take the tangential component of the forces??

 

[radou]

Unfortunately, I can't see the image, but putting the forces into components would be a good start.

 

[merced]

Click on the image.

 

[radou]

Click on the image.

I don't have anything to click on, it's my computer, probably. Someone else will be able to give an exact reply to you. In the meantime, prepare some work to present.

 

[merced]

I guess what I mean is, how do I determine what is perpendicular to the intersection (O)? Because I have to use the perpendicular force right?