What was the name of the voyages taken by Zheng he during the Ming dynasty on behalf of China

Write the function getkthdigit(n, k) that takes a possibly-negative int n and a non-negative int k, and returns the kth digit of n, starting from 0, counting from the right

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.

Explain why electric current cannot exist if a current doesn't have a voltage source.