π |
6 |
令t=sinx,得f(x)=-2t2-t+1=-2(t+
1 |
4 |
9 |
8 |
由二次函數(shù)的圖象,可得當(dāng)t=0或-
1 |
2 |
∴當(dāng)sinx=0或-
1 |
2 |
②當(dāng)x∈[0,
π |
2 |
類似①的計(jì)算,可得:當(dāng)sinx=1時(shí)函數(shù)f(x)的最小值是0
綜上所述,可得當(dāng)x∈[?
π |
6 |
π |
2 |
π |
2 |
故選:A
π |
6 |
π |
2 |
9 |
8 |
1 |
2 |
π |
6 |
1 |
4 |
9 |
8 |
1 |
2 |
1 |
2 |
π |
2 |
π |
6 |
π |
2 |
π |
2 |