 An expression tree, "T", can be evaluated by applying the operator at the root to the values obtained by recursively evaluating the left and right subtrees.An algebraic expression can be produced from a binary expression tree by recursively producing a parenthesized left expression, then printing out the operator at the root, and finally recursively producing a parenthesized right expression.This general strategy (left, node, right) is known as an in-order traversal.