题目
若θ∈[-
π |
12 |
提问时间:2021-03-04
答案
y=cos(θ+
)+sin2θ=cos(θ+
)-cos(2θ+
)
=-cos2(θ+
)+cos(θ+
)
=-2cos2(θ+
)+cos(θ+
)+1
∵θ∈[-
,
],
∴
≤cos(θ+
)≤
π |
4 |
π |
4 |
π |
2 |
=-cos2(θ+
π |
4 |
π |
4 |
=-2cos2(θ+
π |
4 |
π |
4 |
∵θ∈[-
π |
12 |
π |
12 |
∴
1 |
2 |
π |
4 |
|