“怎么如此高兴”常见的英语表达有:Why are you so happy? 或者 How come you are so happy?
“Why are you so happy?”中,“why”表示“为什么”,“are”是系动词“是”,“so”表示“如此,这么”,“happy”意思是“高兴的,快乐的”。
“How come you are so happy?”中,“how come”是一个常用的口语表达,意思是“怎么会,为什么”。
例如:A: Why are you so happy? B: Because I got the job I wanted. (A: 你怎么如此高兴?B: 因为我得到了我想要的工作。)
再比如:A: How come you are so happy? B: I just won the lottery! (A: 怎么如此高兴?B: 我刚中了彩票!)