Is it possible for a triangle with a perimeter of 16 and an area of 11 to be a right triangle?
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Assume that it is possible, and let a and b be the legs of the right triangle.
By the Pythagorean Theorem, the hypotenuse is a 2 + b 2 , so the perimeter would be P = a + b + a 2 + b 2 = 1 6 .
Also, the area would be A = 2 1 a b = 1 1 , which rearranges to b = a 2 2 .
Substituting b = a 2 2 into a + b + a 2 + b 2 = 1 6 gives a + a 2 2 + a 2 + ( a 2 2 ) 2 = 1 6 , which rearranges to 8 a 2 − 7 5 a + 1 7 6 = 0 (for a = 0 ).
However, the discriminant of 8 a 2 − 7 5 a + 1 7 6 = 0 is 7 5 2 − 4 ⋅ 8 ⋅ 1 7 6 = − 7 , so there is no real solution for a .
The original assumption leads to a contradiction, so we can reject it and conclude that such a triangle is not possible .
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Let a , b be the legs of a right triangle and c is the hypotenuse. So, we have, 2 a b a + b + c a 2 + b 2 = 1 1 ⟹ a b = 2 2 = 1 6 ⟹ a + b = 1 6 − c = c 2 ( 1 ) ( 2 ) ( 3 ) Squaring equation ( 2 ) , using equations ( 1 ) and ( 3 ) , ( a + b ) 2 a 2 + b 2 + 2 a b c 2 + 4 4 3 2 c ∴ c = ( 1 6 − c ) 2 = 2 5 6 − 3 2 c + c 2 = 2 5 6 − 3 2 c + c 2 = 2 1 2 = 8 5 3 So equation ( 2 ) transforms to, a + b a + a 2 2 8 a 2 − 7 5 a + 1 7 6 = 8 7 5 = 8 7 5 = 0 In the above quadratic, the discriminant , Δ = ( − 7 5 ) 2 − 4 ⋅ 8 ⋅ 1 7 6 = − 7 < 0 . Hence, the quadratic does not have real solutions and both a , b are complex numbers.
Therefore, there does not exist a right triangle such that its area is 1 1 and perimeter is 1 6 .