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	  Spillway Gate 
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       For safety reasons, most dams are equipped with spillway gates to control
        the water level of the reservoir in the event of a flood. Consider a
        spillway gate that consists a circular arc AB as shown in the figure.
        The arc has a radius of 3 meters and the water level is at 6 meters. The spillway gate is 8 meters wide. 
         
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