题目
△ABC外接圆半径为1,角A、B、C所对的边分别是a、b、c,且角A,B,C成等差数列,求a2+c2的取值范围.
提问时间:2021-04-02
答案
由A、B、C成等差数列,知B=60°由正弦定理有asinA=bsinB=csinC=2R,有b=2RsinB=2×1×32=3,即有b2=a2+c2-2acccosB=a2+c2-2ac×12=a2+c2-ac.即a2+c2=b2+ac>3.且有a2+c2=b2+ac≤3+a2+c2c,所以a2+c2≤6,即a2+c2的...
举一反三
我想写一篇关于奥巴马的演讲的文章,写哪一篇好呢?为什么好
奥巴马演讲不用看稿子.为什么中国领导演讲要看?
想找英语初三上学期的首字母填空练习……
英语翻译
1,人们染上烟瘾,最终因吸烟使自己丧命.
最新试题
热门考点
- 1She took a vacation to America two ears ago(同义句)
- 2X+60+60=X×(1+20%)
- 3Travelling by air may be _______ A.quicker B.more quickly
- 4We took the tram to the park.划took the tram.划线提问
- 5离子的还原性相当于什么?
- 6例3:已知函数fx=ax^2-c,且-4≤f1≤-1,-1≤f2≤5.求f3的取值范围
- 7I believed by the end of that year an advanced version of that software would have been developed,bu
- 8At last he walked _____the forest and saw the village
- 9past tense,present tense,past participle
- 10一缕幽香,谢,