2-8-4 passenger trains. Later, when the line was upgraded with heavier rails, they were transferred to the Moscow-Kursk-Kharkov-Sinelnikovo line. When more class IS locomotives began to roll out from the Voroshilovgrad production lines, they were used on the upgraded Moscow-Smolensk-Minsk, Moscow to Valuiki and Mitchurinsk to Rostov-on-Don mainlines. Only one such locomotive was preserved, no. IS21-578, plinthed outside the main railway station in Kiev in Ukraine. Locomotives of a 2-8-4 wheel arrangement were used mainly for hauling fast express freight trains on heavy freight service. They often replaced older 2-8-2 Mikados where more power was required. In turn, they were often
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