問2題數學題~

The second sets of lengths from a right-angled triangle
since 13^2+84^2=85^2
For the first set
since 30=30
the only possible choice is
25^2=30^2+30^2
but it is not true
So the first set of lengths does not from a right-angled triangle

2007-01-28 18:27:19 補充：
13^2+84^2=85^2=7225

2007-01-28 18:28:53 補充：
下面個位copy and paste 錯佐不過等腰都可以是直角bor

2007-01-28 18:36:26 補充：
For the first setsince two sides are both 30 and 30^2+a^2≠30^2 (if a>0) Also25^2≠30^2+30^2 So the first set of lengths does not from a right-angled triangle

the second one

because the longest side is 85
85^2=7225
13^2+84^2=7225
'.'13^2+84^2=85^2
.'.this set of lengths is from a right-angled triangle(converse of Pyth. Thm)

no.2
because 13^2+ 84^2 = 85^2
By Pyth. Theorem
it is a right-angled triangle.
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why no 1 is not a right angled triangle?
Consider the following calculation:
25^2 + 30^2 NOT = 30^2
30^2 + 30^2 NOT = 25^2
Therefore we can sure that triangle 1 is not right angled.

25,30,30 can form a right angled triangle because the total of the lengths give a size of a right-angled triangle

and 13,84.85 form an isocleles triangle

第二個

畢氏定理

13*13+84*84 = 85*85