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工作学习 / 求学深造 / a math question thanks!! Suppose triangle ABC has side lengths a, b, c, Prove that if a*a+b*b+c*c=ab+bc+ac, then triangle ABC is an equilateral triangle.
-bluefiberglass(ricebox1/2);
2002-1-19
(#340457@0)
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ina*a+b*b>=2*a*b;
b*b+c*c>=2*b*c;
c*c+a*a>=2*c*a;
each = is true only if x==y
2(a*a+b*b+c*c)>=2(a*b+b*c+c*d)
the = is true only if
a==b==c
-blaise();
2002-1-19
{149}
(#340463@0)
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thanks, and another question
-bluefiberglass(ricebox1/2);
2002-1-19
{624}
(#340474@0)
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n*n*n-n*n-4 =(n-2)*(n*n+n+2)
-wxyz(wxyz);
2002-1-20
(#340746@0)
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Why do you do such easy questions? n*n*n-n*n-4=(n-2)(n*n+n+2), so it is a composite number.
-bigsquirrel(小松鼠);
2002-1-20
(#340763@0)
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(a-b)**2+(b-c)**2+(c-a)**2=0这可是基本功啊！！
-wxyz(wxyz);
2002-1-19
{18}
(#340478@0)
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2(a*a+b*b+c*c)=2*(ab+ba+ac)
> (a-b)^2 + (b-c)^2+(a-c)^2=0
>a=b,b=c,a=c
-winger1234(ben);
2002-1-19
(#340550@0)
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too easy. a*a+b*b+c*c if and only if a=b=c>0, no matter a b c are the sides of a triangle or not.
-bigsquirrel(小松鼠);
2002-1-20
(#340750@0)
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你在上几年级？
-urfr(urfr);
2002-1-20
(#340764@0)