Let G1 and G2 be groups, and let G = G1 × G2. Write e and e2 for the identities of G1 and G2 respectively. Let H = {(g1, e2) | gi € G1} and K = {(e1, g92) | g2 E G2}. (a) Prove that H and K are subgroups of G. (b) Prove that HK = KH =G. (c) Prove that HN K = {(e1, e2)}.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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Let \( G_1 \) and \( G_2 \) be groups, and let \( G = G_1 \times G_2 \). Write \( e_1 \) and \( e_2 \) for the identities of \( G_1 \) and \( G_2 \) respectively. Let \( H = \{(g_1, e_2) \mid g_1 \in G_1\} \) and \( K = \{(e_1, g_2) \mid g_2 \in G_2\} \).

(a) Prove that \( H \) and \( K \) are subgroups of \( G \).

(b) Prove that \( HK = KH = G \).

(c) Prove that \( H \cap K = \{(e_1, e_2)\} \).
Transcribed Image Text:Let \( G_1 \) and \( G_2 \) be groups, and let \( G = G_1 \times G_2 \). Write \( e_1 \) and \( e_2 \) for the identities of \( G_1 \) and \( G_2 \) respectively. Let \( H = \{(g_1, e_2) \mid g_1 \in G_1\} \) and \( K = \{(e_1, g_2) \mid g_2 \in G_2\} \). (a) Prove that \( H \) and \( K \) are subgroups of \( G \). (b) Prove that \( HK = KH = G \). (c) Prove that \( H \cap K = \{(e_1, e_2)\} \).
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