a formal announcement的用法和样例：
- I hope that we might wait until April of 1999 to make a formal announcement of this exciting project.
- The bid was put to Unesco officials in Paris on October 13th and a formal announcement was made on 14th.
- Solskjaer, who joined United from Molde in a ?.5million deal in 1996, is expected to make a formal announcement on Tuesday.
- McCain is expected to make a formal announcement shortly at a rally in (the midwestern city of) Dayton, Ohio, ahead of next week's Republican National Convention.
- Lei Yi: I also heard the news in 1977, has not started a formal message, and no formal announcement, the grapevine is to begin, we just do not believe that.