Place:Our classroom
Time:2 P. m. July 8th, Wednesday
Activities:sing songs;chat;take photos;have some cakes, chocolates, juice and fresh fruits
(Ⅰ)求 OA→ , OB→ 夹角的余弦值;
(Ⅱ)已知C(1,0),记∠AOC=α,∠BOC=β,求tan α+β2 的值.
充分接纳自己,提高自制力,是有知识、有理性、有自信和有自知之明的表现。( )
写作:____ 表示____个十和____个一。