【Claire Pan】評論
-1≦sinA≦1-1≦cosA≦1secA≦-1 or secA≧1cseA≦-1 or cscA≧1-1/2≦sinA x cosA ≦1/2-根號2≦sina + cosA ≦根號2
【Ihou Vivian】評論
(sin ^2x + 4sinx +4)+1=(sin x+2)^2+1當sinx=-1, (sin x +2)^2+1有最小值 2