code: function(expr, context, subIntegral) {
        if(expr.type === 'OperatorNode' && expr.op === '^') {
          var base = expr.args[0];
          var exponent = expr.args[1];
          if(base.type === 'OperatorNode' && base.op === '*') {
            return subIntegral(new OperatorNode('*', 'multiply', base.args.map(function(baseChild) {
              return new OperatorNode('^', 'pow', [baseChild, exponent]);
            })), context, "distributing power");
          }
        }
      }
docs: integral((f(x) * g(x))^h(x), x) = integral(f(x)^h(x) * g(x)^h(x))