-1≦sinA≦1
-1≦cosA≦1
secA≦-1 or secA≧1
cseA≦-1 or cscA≧1
-1/2≦sinA x cosA ≦1/2
-根號2≦sina + cosA ≦根號2
(sin ^2x + 4sinx +4)+1=(sin x+2)^2+1
當sinx=-1, (sin x +2)^2+1有最小值2
sin ^2x + 4sinx +5 的最小值為(A)1 (B)2 (C)5 (..-阿摩線上測驗