MHB Find the lengths of the sides of a triangle

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To find the lengths of the sides of a triangle given the altitudes of 14, 22, and 28, one can use the relationship between the area of the triangle and its altitudes. The area can be expressed using each altitude and the corresponding side length. By applying the formula for the area (Area = 1/2 * base * height) for each altitude, the side lengths can be calculated. The side lengths will be proportional to the inverses of the altitudes. Ultimately, the side lengths of the triangle are determined through these calculations.
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Find the lengths of the sides of a triangle with 14, 22 and 28 as the lengths of its altitude.
 
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anemone said:
Find the lengths of the sides of a triangle with 14, 22 and 28 as the lengths of its altitude.

let the lengths opposite to altitudes of lengths 14,22,28 be x,y,z
then 2 times area
$14x = 22 y = 28 z$
or $x:: y:: z = \frac{1}{14}::\frac{1}{22}:: \frac{1}{28} = 44::28:: 22$(note all kept even to avoid fraction in computation )
so let x= 44t, y = 28t, z = 22t
area = $\dfrac{14x}{2}= 7x = 7 * 44 t = 308t$
using heros formula ( we get $s= \frac{44+28+22}{2}=47$)
$area = \sqrt{47*(47-44)*(47-28)*(47-22)}t^2 = \sqrt{47* 3 * 19* 25}t^2$
or $area = 5\sqrt{47*57}= 5\sqrt{2679}t^2$
so $308t = 5 \sqrt{2679}t^2$
or $t=\frac{308}{5\sqrt{2679}}$
so the sides are
$44t,28t,22t$ where t is as above
 
Last edited:
kaliprasad said:
let the lengths opposite to altitudes of lengths 14,22,28 be x,y,z
then 2 times area
$14x = 22 y = 28 z$
or $x:: y:: z = \frac{1}{14}::\frac{1}{22}:: \frac{1}{28} = 44::28:: 22$(note all kept even to avoid fraction in computation )
so let x= 44t, y = 28t, z = 22t
area = $\dfrac{14x}{2}= 7x = 7 * 44 t = 308t$
using heros formula ( we get $s= \frac{44+28+22}{2}=47$)
$area = \sqrt{47*(47-44)*(47-28)*(47-22)}t^2 = \sqrt{47* 3 * 19* 25}t^2$
or $area = 5\sqrt{47*57}= 5\sqrt{2679}t^2$
so $308t = 5 \sqrt{2679}t^2$
or $t=\frac{308}{5\sqrt{2679}}$
so the sides are
$44t,28t,22t$ where t is as above

Well done, kaliprasad!
 
a = 52.3657142876
b = 33.3236363648
c = 26.1828571438

From Wikipedia:
"Next, denoting the altitudes from sides a, b, and c respectively as ha, hb, and hc, and denoting the semi-sum of the reciprocals of the altitudes as H = (h_a^{-1} + h_b^{-1} + h_c^{-1})/2 we have[11]
A^{-1} = 4 \sqrt{H(H-h_a^{-1})(H-h_b^{-1})(H-h_c^{-1})}."
 
Last edited by a moderator:
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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