11.80: a) The torque exerted by the cable about the left end is . For any angle TLsinθ
so the tension T will be the same for either angle. The horizontal ？, sin(180，;θ)；sinθ,
component of the force that the pivot exerts on the boom will be
1T α ,. b) From the result of part (a), and this T cosθ or Tcos (180，;？)；;Tcosθsinθ
becomes infinite as Also, c), the tension is a minimum when is a ？？0 or ？180，.sin ？
maximum, or a vertical string. d) There are no other horizontal forces, so for the ？；90，,
boom to be in equilibrium, the pivot exerts zero horizontal force on the boom.