急死了在△ABC中asinA+csinC-根号2asinC=bsinB,求B函数f(x)=x*3+3ax*2+(3-6a)x-12a-4证明:1:f(x)在x=0切点过(2,0):2:若f(x)在x=x0处取最小值,x0属于(1,3),求a的取值范围再帮我一道题
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![急死了在△ABC中asinA+csinC-根号2asinC=bsinB,求B函数f(x)=x*3+3ax*2+(3-6a)x-12a-4证明:1:f(x)在x=0切点过(2,0):2:若f(x)在x=x0处取最小值,x0属于(1,3),求a的取值范围再帮我一道题](/uploads/image/z/2512010-2-0.jpg?t=%E6%80%A5%E6%AD%BB%E4%BA%86%E5%9C%A8%E2%96%B3ABC%E4%B8%ADasinA%2BcsinC-%E6%A0%B9%E5%8F%B72asinC%3DbsinB%2C%E6%B1%82B%E5%87%BD%E6%95%B0f%28x%29%3Dx%2A3%2B3ax%2A2%2B%EF%BC%883-6a%29x-12a-4%E8%AF%81%E6%98%8E%EF%BC%9A1%EF%BC%9Af%28x%29%E5%9C%A8x%3D0%E5%88%87%E7%82%B9%E8%BF%87%EF%BC%882%2C0%EF%BC%89%3A2%EF%BC%9A%E8%8B%A5f%28x%29%E5%9C%A8x%3Dx0%E5%A4%84%E5%8F%96%E6%9C%80%E5%B0%8F%E5%80%BC%2Cx0%E5%B1%9E%E4%BA%8E%EF%BC%881%2C3%EF%BC%89%EF%BC%8C%E6%B1%82a%E7%9A%84%E5%8F%96%E5%80%BC%E8%8C%83%E5%9B%B4%E5%86%8D%E5%B8%AE%E6%88%91%E4%B8%80%E9%81%93%E9%A2%98)
急死了在△ABC中asinA+csinC-根号2asinC=bsinB,求B函数f(x)=x*3+3ax*2+(3-6a)x-12a-4证明:1:f(x)在x=0切点过(2,0):2:若f(x)在x=x0处取最小值,x0属于(1,3),求a的取值范围再帮我一道题
急死了在△ABC中asinA+csinC-根号2asinC=bsinB,求B
函数f(x)=x*3+3ax*2+(3-6a)x-12a-4证明:
1:f(x)在x=0切点过(2,0):
2:若f(x)在x=x0处取最小值,x0属于(1,3),求a的取值范围
再帮我一道题
急死了在△ABC中asinA+csinC-根号2asinC=bsinB,求B函数f(x)=x*3+3ax*2+(3-6a)x-12a-4证明:1:f(x)在x=0切点过(2,0):2:若f(x)在x=x0处取最小值,x0属于(1,3),求a的取值范围再帮我一道题
根据正弦定理,设a/sinA=b/sinB=c/sinC=k
则sinA=a/k sinB=b/K sinC=c/k
代入已知条件 asinA+csinC-根号2asinC=bsinB
得 a^2+c^2-√2ac=b^2
由余弦定理 a^2+c^2-2accosB=b^2
故cosB=√2/2
B=45°
解
根据正弦定理,a/sinA=b/sinB=c/sinC,则
sinA=(a/b)sinB
sinC=(c/b)sinB
asinA+csinC-√2asinC=bsinB
(a^2/b)sinB+(c^2/b)sinB-√2(ac/b)sinB=bsinB
a^2/b+c^2/b-√2(ac/b)=b
a^2+c^2-√2ac=b^2
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解
根据正弦定理,a/sinA=b/sinB=c/sinC,则
sinA=(a/b)sinB
sinC=(c/b)sinB
asinA+csinC-√2asinC=bsinB
(a^2/b)sinB+(c^2/b)sinB-√2(ac/b)sinB=bsinB
a^2/b+c^2/b-√2(ac/b)=b
a^2+c^2-√2ac=b^2
a^2+c^2-b^2)/(ac)=√2
根据余弦定理:b^2=a^2+c^2-2accosB,可得
cosB=(a^2+c^2-b^2)/(2ac)=√2/2
B=45°
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a/sinA=b/sinB=c/sinC 所以得:sinA=asinB/b sinC=csinB/b 带入式中 化简可得:(a^2+c^2-b^2)/2ac=√2/2 即是 cosb=√2/2 所以B=45°函数f(x)=x*3+3ax*2+(3-6a)x-12a-4证明: 1:f(x)在x=0切点过(2,0): 2:若f(x)在x=x0处取最小值,x0属于(1,3),...
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a/sinA=b/sinB=c/sinC 所以得:sinA=asinB/b sinC=csinB/b 带入式中 化简可得:(a^2+c^2-b^2)/2ac=√2/2 即是 cosb=√2/2 所以B=45°
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