# How do you use Heron's formula to find the area of a triangle with sides of lengths #9 #, #5 #, and #11 #?

##### 1 Answer

Mar 15, 2016

≈ 22.185

#### Explanation:

This is a two step process

step 1 : Find half the perimeter (s) of the triangle

step 2 : calculate the area (A)

let a = 9 , b = 5 and c = 11

step 1 : s

#= (a+b+c)/2 = (9+5+11)/2 = 25/2 = 12.5 # step 2 :

#A = sqrt(s(s-a)(s-b)(s-c))#

# = sqrt(12.5(12.5-9)(12.5-5)(12.5-11))#

#rArr A = sqrt(12.5xx3.5xx7.5xx1.5) ≈ 22.185#