(commence array l Rightarrow sin Acos C + sin Ccos A = 2cos Asin C Leftrightarrow sin Acos C = cos Asin C;(*)conclude array )(start off array l A subset B Leftrightarrow forall x inside of a Rightarrow x in BA notsubset B Leftrightarrow exists x within a Rightarrow x notin Bend array )Xem th? ?? Toán ten Cánh di?u Ch? t? 200k mua tr?n b? ?? thi T