作者jjx66os (igor)
看板trans_math
标题[多变] 一题二元变数极值
时间Sat Jun 2 16:24:52 2012
Find the local maximum and minimum values and saddle points of the fuction.
f(x,y)= sinx + siny + sin(x+y) , 0<x<2π,.0<y<2π
最大问题是critical points 要怎麽求?
Fx= cosx + cos(x+y)
Fy= cosy + cos(x+y)
令Fx=Fy=0
我目前只能找到(x,y)=(π,π)
其他的点就不知道怎麽去找了，希望高手指教，谢谢！
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※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 61.225.206.220
1F：→ suhorng:cos(x) + cos(x+y) = 2cos(x+y/2)cos(y/2) 61.217.34.17 06/02 21:48
2F：→ suhorng:cos(y) + cos(x+y) = 2cos(x/2+y)cos(x/2) 61.217.34.17 06/02 21:48
3F：→ jjx66os:资质驽钝，这算是技巧吗，可否解释一下?谢 61.225.197.186 06/02 23:14
4F：→ BaBi:积化合差 218.163.91.47 06/02 23:34
5F：→ BaBi: 和 218.163.91.47 06/02 23:35
6F：→ BaBi:2cos(a)cos(b) = cos(a+b)+cos(a-b) 218.163.91.47 06/02 23:35
7F：→ BaBi:聪明的你应该知道a,b各取什麽了XDD 218.163.91.47 06/02 23:36
8F：→ jjx66os:感谢XD 61.225.197.186 06/03 00:15
9F：→ jjx66os:其实我发现找出x=y，再带回去也可以耶，总 61.225.197.190 06/03 23:35
10F：→ jjx66os:之感谢两位大大了 61.225.197.190 06/03 23:35