Что называют молекулов вещества?

почему язык можно назвать одеждой мысли

Why should children follow rules? Fill in the gaps with the correct preposition.

Safety rules _____ children help children to learn how to be safe in difficult situations. Your parents care _____ your safety and they think ______ you. They think you should be cautious _____ strangers,  you should check _____ them and get ______ permission before you go anywhere.

Найдите: tgα, если cosα=1/√5 и 0< α <π/2

1)1/√5;   2)2;   3)1/2;   4)√5