Magnitude and Direction of Force

[chadovP]

Homework Statement

http://img243.imageshack.us/my.php?image=61581222vi0.jpg
http://xs433.xs.to/xs433/08440/untitled601.jpg

I need to find the direction and the magnitude of F3 given only the figure and the resultant force of the 3 vectors =20 lb, plus F3 being the smallest force between all of them.

The Attempt at a Solution

Tried Rx and Ry and squaring them but I have 3 unknows in 1 solution...

any ideas?

 

[tiny-tim]

Welcome to PF!

Tried Rx and Ry and squaring them but I have 3 unknows in 1 solution...

Hi chadovP! Welcome to PF!

(have a theta: θ )

I don't get it …

the only two unknowns are F₃ and θ …

what unknowns did you have?

 

[chadovP]

yes but there are sin θ and cos θ which makes the equation very complicated.

 

[tiny-tim]

yes but there are sin θ and cos θ which makes the equation very complicated.

ah!

but that's still only one unknown!

Hint: square, and add.

 

[chadovP]

2 unknows mate! F3 and the angle...
so i have f3 sqaured and the angle in one equation and that the part i am not getting...

 

[tiny-tim]

square, and add!