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The solid lies between planes perpendicular to the $$x$$ -axis at $$x = - 1$$ and $$x = 1$$ . The cross-sections perpendicular to the $$x$$ -axis between these planes are squares whose bases run from the semicircle $$y = - \sqrt { 1 - x ^ { 2 } }$$ to the semicircle $$y = \sqrt { 1 - x ^ { 2 } }$$
$$16 / 3$$