Answer:
B. II (6, 8, 10)
Explanation:
A set of triangle side lengths will form a right triangle if they satisfy the Pythagorean theorem. The sum of squares of the shortest two sides must equal the square of the longest side.
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Pythagorean triples
Sets of integers that satisfy the Pythagorean theorem are called "Pythagorean triples." Some of these for smaller integers are ...
(3, 4, 5), (5, 12, 13), (7, 24, 25), (8, 15, 17)
If small integer side lengths are not one of these triples, or a multiple of one of these triples, they will not form a right triangle.
I. not a match to any triple
II. matches (3, 4, 5) multiplied by 2 -- a right triangle
III. not a match to any triple
IV. not a match to any triple
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Pythagorean equation
Of course, you can actually compute the squares to see if they satisfy the Pythagorean theorem:
I. 4² +5² = 41 ≠ 6² (acute triangle)
II. 6² +8² = 100 = 10² -- right triangle
III. 5² +13² = 194 ≠ 14² (obtuse triangle)
IV. 7² +11² = 170 ≠ 13² (acute triangle)
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form factor
The sum f = a² +b² -c² (where c is the longest side) can be considered to be a "form factor" for the triangle. For ...
- f>0, the sides form an acute triangle
- f=0, the sides form a right triangle
- f<0, the sides form an obtuse triangle
This "form factor" is related to the largest angle (C) by ...
cos(C) = f/(2ab)