抽象代數-conjugate&normal subgroup

1.
Suppose that a is conjugate to b in a group G.
Show that C(a) is also conjugate to C(b) in G

其中C(a)={ g屬於G | ga=ag }

2.
Show that if H and K are normal subgroups of a group G such that

H聯集K={e} , then hk=kh for all h屬於H and k屬於K
Update: To 淡淡:
這樣不是只有證明b和C(a) conjugate嗎?
還是其實已經證C(a)和C(b) conjugate了...?
可以說明一下嗎?謝謝~
Update 2: !!!
我看懂了
3 answers 3