4 A bag of cement whose weight \( F_{g} \) hangs in equilibrium from three wires as shown below. Two of the wires make angles \( \theta_{1} \) and \( \theta_{2} \) with the horizontal. Assuming the system is in equilibrium, show that the tension in the left-hand wire is
(8)
\[
T_{1}=\frac{F_{g} \cos \theta_{2}}{\sin \left(\theta_{1}+\theta_{2}\right)}
\]
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