The area of a triangle ABC is 126 sq.cm.

Question

AC=13 cm , BC = 21 cm, what is the length of AB?
where, triangle ABC is a scalene triangle

Answer 1

I'd use Heron's formula. Here, if c is the length of AB,

s = (34+c)/2 = 17 + c/2

so we have

(17+c/2)(4+c/2)(-4+c/2)(17-c/2) = 126^2

It looks messy, but expands into a nice simple quadratic in c^2.

c=20

Answer 2

Introduce values triancal.esy.es/?a=21&b=13&t=126
c = 20 or
c = 28.6356421265
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