Tā shénsè tàirán, hǎoxiàng shénme shì dōu méi fāshēng guo.
He looked completely at ease, as if nothing had happened.
Tips
usage
泰然 is a written word that lives mostly in set phrases: 泰然自若 (calm and self-possessed), and 泰然处之 or 处之泰然 (to take something calmly). In conversation, 淡定 or 冷静 is more usual.
