Two corners of an isosceles triangle are at (8 ,2 )(8,2) and (4 ,3 )(4,3). If the triangle's area is 9 9, what are the lengths of the triangle's sides?

2 Answers
Jun 10, 2018

color(indigo)("Isosceles triangle's sides are " 4.12, 4.83, 4.83Isosceles triangle's sides are 4.12,4.83,4.83

Explanation:

![https://www.algebra.com/algebra/homework/Geometry-proofs/Geometry_proofshttp://.faq.question.209023.html](https://useruploads.socratic.org/AM7WAi4Tzyrvy0qBVAcz_isosceles%20triangle.jpg)

A(8,2), B(4,3), A_t = 9A(8,2),B(4,3),At=9

c = sqrt(8-4)^2 + (3-2)^2) = 4.12c=842+(32)2)=4.12

h = (2 * A_t) / c = (2 * 9) / 4.12 = 4.37h=2Atc=294.12=4.37

a = b = sqrt((4.12/2)^2 + 4.37^2) = 4.83a=b=(4.122)2+4.372=4.83

Jun 10, 2018

Base \sqrt{17}17 and common side sqrt{1585/68}.158568.

Explanation:

They're vertices, not corners. Why do we have the same bad wording of the question from all around the world?

Archimedes' Theorem says if A,B and CA,BandC are the squared sides of a triangle of area SS, then

16S^2 = 4AB-(C-A-B)^216S2=4AB(CAB)2

For an isosceles triangle, A=B.A=B.

16S^2 = 4A^2-(C-2A)^2 = 4AC-C^216S2=4A2(C2A)2=4ACC2

We're not sure if the given side is AA (the duplicated side) or CC (the base). Let's work it out both ways.

C = (8-4)^2 + (2-3)^2 = 17C=(84)2+(23)2=17

16(9)^2 = 4A(17) - 17^2 16(9)2=4A(17)172

A = 1585/68A=158568

If we started with A=17A=17 then

16(9)^2 = 4(17)C - C^2 16(9)2=4(17)CC2

C^2 - 68 C + 1296 = 0 C268C+1296=0

No real solutions for that one.

We conclude we have base \sqrt{17}17 and common side sqrt{1585/68}.158568.