Let C be the field of complex numbers and C ^ * be the group of non-ze...
Understanding the Properties of C and C^*
The field of complex numbers, denoted as C, and the group of non-zero complex numbers under multiplication, denoted as C^*, have unique properties. Let's analyze the given statements.
(a) C is cyclic
- C is not cyclic because it is an infinite-dimensional vector space over the real numbers. A cyclic group can be generated by a single element, which is not possible for the entire field of complex numbers. Thus, this statement is false.
(b) Every finite subgroup of C^* is cyclic
- Every finite subgroup of C^* is indeed cyclic. This is a consequence of the structure theorem for finite abelian groups, where finite subgroups of C^* can be expressed as roots of unity. Hence, this statement is true.
(c) C^* has finitely many finite subgroups
- C^* contains infinitely many finite subgroups, as it includes all nth roots of unity for any integer n. Each set of nth roots of unity forms a distinct finite subgroup. Therefore, this statement is false.
(d) Every proper subgroup of C^* is cyclic
- This statement is not universally true. While all finite subgroups are cyclic, infinite proper subgroups may not be. For instance, the subgroup of all non-zero complex numbers with a fixed modulus (which is infinite) is not cyclic. Thus, this statement is false.
Summary of Truth Values
- (a) False
- (b) True
- (c) False
- (d) False
In conclusion, only statement (b) holds true in the context of complex numbers and their multiplicative group.
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