I am sure if they mean the same. If there are some differences between them, what are those? When and how to use each of them? Thanks.
1 Answer
They don't mean the same.
"你去干嘛?" means "What are you going to do?" or maybe "Why are you going?" depending on the context.
"你去吗?" means "Are you going?"
Examples:
A: 我出去一会 = I'm leaving for a while. B: 你去干嘛? = What are you going to do?
A: 我去开会了 = I'm going to attend the meeting. B: 这会是给经理开的, 你去干嘛? = The meeting is intended for managers. Why are you going?
A: 我要去吃午饭, 你去吗 = I'm leaving for lunch. Are you going (with me)?