§和角公式
... ( tan( (,tan( tan( ( (1) tan(( ( () (( 5 (2) cos2(( ( () ( (3) 3sin2(( ( () ( 5sin(( ( ( ) cos(( ( () ( 2cos2 ... ( 0 ( A ( C,故(ABC為等腰三角形 12.在 ABC中,sinA ( sinB ( cosC (,求(C之角度。 【解答】(C ( 120( 【詳解】∵ sinA ( sinB ( cosC ) ( ( 2cos cos( 2 cos ......