mistaken 后面可以接不定式，则表示做某事是不对的或错误的。如：

He was mistaken to have told her. 他告诉了她，这是他的不对。

You are mistaken not to have told us. 你没有告诉我们，这就是你的不对了。

另外，mistaken 后面还经常接 in doing，这类搭配多见于thinking, believing, supposing, assuming 等 -ing 动词。如：

I was mistaken in believing him. 我相信了他，这是不对的。

She is mistaken in thinking that the report was written last year. 她错误地认为那份报告是去年写的。

同意千千老师的解答。我在葛传槼等人编的《简明英语惯用法》中找到了一个后接不定式的例句：