4-8-8-2 leading truck sits under the smokebox and the trailing truck under the firebox. On a cab-forward, the leading truck supports the firebox and the trailing truck and smokebox are at the rear next to the tender. A 4-8-8-2 is effectively a 2-8-8-4 that always runs in reverse. Although commonly called "Mallets" these cab-forwards were built with simple expansion cylinders. The name stuck because the original classes of Southern Pacific cab-forwards were built as compound Mallets, though these were also eventually converted to simple expansion. The Southern Pacific was the only railroad to operate engines of this wheel arrangement. All were
1/2 + 1/4 + 1/8 + 1/16 + ⋯ 1/2 + 1/4 + 1/8 + 1/16 + ⋯ In mathematics, the infinite series is an elementary example of a geometric series that converges absolutely. There are many different expressions that can be shown to be equivalent to the problem, such as the form: 2 + 2 + 2 + ... The sum of this series can be denoted in summation notation as: As with any infinite series, the infinite sum is defined to mean the limit of the sum of the first terms as approaches infinity. Multiplying by 2 reveals a useful relationship: Subtracting from both sides, As approaches