唔識做功課47

0度 ≤ b ≤ 90度
sin 0度 ≤ sin b ≤ sin 90
0 ≤ sin b ≤ 1
0 ≤ sin^2 b ≤ 1
3 ≤ 3 + sin^2 b ≤ 3 + 1
1/3 ≥ 1/(3 + sin^2 b) ≥ 1/4
2/3 ≥ 2/(3 + sin^2 b) ≥ 2/4
2/3 ≥ 2/(3 + sin^2 b) ≥ 1/2∴ the maximum value of 2/(3 + sin^2 b) is 2/3.

你其實可以問老師,而且你問題有小小不清晰=.=