题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064719-86858.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064719-17132.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064719-71385.gif)
在
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064720-21265.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064720-95723.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064720-47717.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064720-20016.gif)
(I)求角B的大小;
(Ⅱ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-96478.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-22000.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-51378.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064720-21265.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-32447.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-87479.gif)
∴2
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064722-19869.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064722-16187.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064722-78411.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064722-75187.gif)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064723-89030.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064723-90558.gif)
(II)由
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-96478.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-22000.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064721-51378.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064723-29903.gif)
由正弦定理得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064723-87648.gif)
又由余弦定理得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064724-13179.gif)
故
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064724-47353.gif)
故△ABC为正三角形 …………12分
故
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064724-47640.gif)
解析
核心考点
试题【(本题满分13分)已知向量与向量的夹角为,在中,所对的边分别为且.(两题改编成)(I)求角B的大小;(Ⅱ)若是和的等比中项,求的面积。】;主要考察你对平面向量数量积的意义等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064708-42945.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064708-76989.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064709-38901.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064709-36643.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064709-39124.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064709-20502.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064709-69245.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064659-50196.png)
A.30° | B.45° | C.60° | D.90° |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064651-90526.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064651-33421.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064651-30726.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064651-83458.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064652-47766.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064652-70985.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064652-63258.gif)
(Ⅰ)求
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064652-25131.gif)
(Ⅱ)判断
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064651-90526.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064643-85615.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064643-81563.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064644-83101.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064644-30544.png)
A.![]() ![]() | B.![]() | C.![]() ![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064635-46459.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064636-52683.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064635-46459.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064636-52683.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064635-46459.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064636-52683.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064636-46192.png)
A
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064636-59415.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064636-83111.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064637-43642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104064637-18759.png)
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