题干
. How pleased the detective was _____ what his customer told him!
A：hearing
B：heard
C：to hearing
D：to hear
答案(点此获取答案解析）
D
A：hearing
B：heard
C：to hearing
D：to hear
(
<β<π)，且sin(α＋β)＝cosα，则tan(α＋β)＝( )