4-8-2+2-8-4 4-8-2+2-8-4 Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a is a Garratt articulated locomotive consisting of a pair of engine units back to back, with the boiler and cab suspended between them. The wheel arrangement has four leading wheels on two axles, usually in a leading bogie, eight powered and coupled driving wheels on four axles and two trailing wheels on one axle, usually in a trailing truck. Since the type is generally known as a Mountain, the corresponding Garratt type is usually known as a Double Mountain. A Garratt locomotive is actually two
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