Sigma is the eighteenth letter of the ancient Greek alphabet. As an upper case letter (Σ), it is used as a symbol for sums and series. As a lower case letter (σ) it is a prefix used in several contexts to indicate that a term is referred in some way to countable unions. For example, a σ-algebra is a collection of sets closed under countable union and a σ-compact topological space is a topological space which is the union of countably many compact subsets. The symbol σ_k(n) is also used to denote the divisor function.
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My son was suffering from low confidence in his educational abilities. I was in need of help and quick. Club Z! assigned Charlotte (our tutor) and we love her! My son’s grades went from D’s to A’s and B’s.
I’ve been using Club Z’s online classrooms to receive some help and tutoring for 2 of my college classes. I must say that I am very impressed by the functionality and ease of use of their online App. Working online with my tutor has been a piece of cake. Thanks Z.
Jonathan is doing really well in all of his classes this semester, 5 A’s & 2 B’s (he has a computer essentials class instead of PLC). In his Algebra class that Nathan is helping him with he has an A+.
Sarah is very positive, enthusiastic and encourages my daughter to do better each time she comes. My daughter’s grade has improved, we are very grateful for Sarah and that she is tutoring our daughter. Way to go ClubZ!
