Be + ADJECTIVE + TO VERB

Be + ADJECTIVE + TO VERB

Adjective can be used, such as : glad, sad, worried, angry, pleased, delighted, disappointed, shocked, afraid, unable, willing, sure, anxious, able, eager, etc.
Examples :

1. 1. I was sorry when/because I heard the bad news.

= I was sorry to hear the bad new.

1. 1. He is ready to go.
   2. I am glad to meet you.
   3. To understand this lesson is easy.

It is easy to understand this lesson.
* It is possible that he telephoned while we were out (= he may have telephoned)