I found this area

Geometry Level 4

In a right triangle, the difference of its hypotenuse and base is 50 cm and the difference of its hypotenuse and perpendicular is 1 cm. Find the area of the incircle of the triangle.

Give your answer upto 2 decimal places.


The answer is 78.57.

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2 solutions

Shubham Poddar
Jan 6, 2018

The area of the incircle of a right triangle is given by π ( h b ) ( h p ) 2 \frac{π(h-b)(h-p)}{2} , where h, p and b are the hypotenuse, height and base of the right triangle respectively.

Marta Reece
Mar 26, 2017

To solve this, I had to assume that what is referred to as "base" and "perpendicular" are the legs of the right triangle in question.

Relationships between the hypotenuse h h , base b b , and perpendicular p p are: h b = 50 , h p = 1 h-b=50, h-p=1 , and p 2 + b 2 = h 2 . p^2+b^2=h^2.

Solving for h h we get two solutions: h = 61 h=61 and h = 41 h=41 . Calculating b b from the second one of those will give us a negative number, so this is not geometrically reasonable.

Using the first solution, we have b = 11 , p = 60 b=11, p=60 , the area of the triangle A = 1 2 p b = 330 A=\frac{1}{2}pb=330 , and semiperimeter s = 1 2 ( b + p + h ) = 66 s=\frac{1}{2}(b+p+h)=66 .

Radius of incircle R = A s = 5 R=\frac{A}{s}=5 . Area of incircle is therefore 25 π 25\pi .

It would be a help to at least some of us if you would change the wording to a more standard terminology.

Marta Reece - 4 years, 2 months ago

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