(get started array l Rightarrow sin Acos C + sin Ccos A = 2cos Asin C Leftrightarrow sin Acos C = cos Asin C;(*)stop array )(start out array l A subset B Leftrightarrow forall x in a very Rightarrow x in BA notsubset B Leftrightarrow exists x inside of a Rightarrow x notin Bconclusion array )T?t C?Tin H?c L?p 6Tin H?c L?p 7Tin H?c L?p 8Tin H?c L?p