Given that ABC is an Isosceles triangle and AD is a median of length of \(5\sqrt{2}\)
To find the perimeter of triangle ABC
Statement 1: AD = BD = CD
Let \(\angle{DAC} = x\)
Then \(\angle{DAC} = \angle{DAB} = \angle{ABD} = \angle{ACD} = x\)
In \(\triangle{DAC}: \) x + x + x + x = 180 (Sum of angles of a triangle = \(180^o\))
\(4x = 180^o\), or \(x = 45^o\)
The triangle is an isosceles right angled triangle, right angled at A and hypotenuse BC = \(5\sqrt{2}+ 5\sqrt{2} = 10\sqrt{2}\)
The equal sides AC = AB = \(\frac{1}{\sqrt{2}} * Hypotenuse = 10\)
Therefore the perimeter = \(10 + 10 + 10\sqrt{2} = 20 + 10\sqrt{2}\)
Statement 1 is sufficient.. The answer Options could be A or D
Statement 2: Triangle ABC is right angled at A
Since it is right angled at A, again we have an isosceles right angled triangle, with \(\angle A = 90^o and \angleB = \angle C = 45^o\)
Therefore, the median from A is a perpendicular bisector and an angular bisector. (Property of an isosceles triangle for the median to the unequal side)
\(\triangle{ABD}\) is an isosceles right angled triangle, with AD = BD = \(5\sqrt{2}\)
\(\triangle{ADC}\) is an isosceles right angled triangle, with AD = DC = \(5\sqrt{2}\)
\(\triangle{ABC}\) is an isosceles right angled triangle, with AB = AC and hypotenuse = \(5\sqrt{2} + 5\sqrt{2} = 10\sqrt{2} \)
The equal sides AC = AB = \(\frac{1}{\sqrt{2}} * Hypotenuse = 10\)
Therefore the perimeter = \(10 + 10 + 10\sqrt{2} = 20 + 10\sqrt{2}\)
Statement 2 is sufficient..
Option DArun Kumar
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