SOLUTION: Triangle ABC is isosceles, with Line AB=AC, and Line BC=39 cm A square is inscribed in the triangle with edges 21 cm. Find the area of Triangle ADE Diagram: https://imgur.com/a/

Algebra ->  Triangles -> SOLUTION: Triangle ABC is isosceles, with Line AB=AC, and Line BC=39 cm A square is inscribed in the triangle with edges 21 cm. Find the area of Triangle ADE Diagram: https://imgur.com/a/      Log On


   



Question 1188247: Triangle ABC is isosceles, with Line AB=AC, and Line BC=39 cm A square is inscribed in the triangle with edges 21 cm. Find the area of Triangle ADE
Diagram: https://imgur.com/a/1RtmfbC

Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
Triangles ADE and ABC are similar, and the similarity coefficient is 21%2F39+=+7%2F13.
Let h be the altitude of the triangle ADE; then the altitude of the triangle ABC is +%28h%2B21%29 centimeters.
The ratio of altitudes is the same
h%2F%28h%2B21%29+=+7%2F13

It gives
13h+=+7%2A%28h%2B21%29
13h+=+7h+%2B+7%2A21
13h+-+7h+=+147
6h+=+147
h+=+147%2F6
h=+24.5cm
Thus the height of the smaller triangle ADE is h=24.5cm; then the height of the larger triangle is h%2B21=24.5%2B21+=+45.5cm
Now you know the base of the triangle ADE DE+=21cm and its height of h=24.5cm, t hen its area of the smaller triangle ADE is
A=%281%2F2%29%2A21cm%2A24.5cm+=+257.2cm%5E2+