sau đó tính ra được là x=1 và x=y=1

Read the fairy tale Cinderella and choose the best answer.

Once upon a time there was a young girl called Cinderella. Cinderella was living happily with her family when her mother died. Her father married an evil widow with two daughters. Cinderella’s stepmother and two stepsisters mistreated her. She had to wear old clothes and work hard while the sisters wore fancy clothes and had fun. A good witch helped Cinderella. She turned Cinderella’s old dress into a beautiful gown. Cinderella went to a party and a handsome prince politely invited her to dance with him. He fell in love with her and wanted to find out who she was. Cinderella left the party in a hurry and didn’t tell the prince her name. But she left a glass slipper, and the prince used that to find her. They got married and lived happily ever after.

Question: Cinderella’s father married a………woman.

A. nice

B. beautiful

B. beautiful

D. evil

Cho hình chóp tam giác đều S.ABC có cạnh đáy bằng a, đường cao S H = a 3 3  Tính góc giữa cạnh bên và mặt đáy của hình chóp

A.  45 o

B.  30 o

C.  75 o

D.  60 o