# How do you use Heron's formula to determine the area of a triangle with sides of that are 35, 28, and 21 units in length?

##### 1 Answer

Jan 16, 2016

#### Explanation:

First, determine the semiperimeter

#s=(a+b+c)/2#

We know that

#s=(35+28+21)/2=42#

Plug these into Heron's formula, which determines the area of a triangle:

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

#A=sqrt(42(42-35)(42-28)(42-21))#

#A=sqrt(42xx7xx14xx21)#

#A=sqrt(2^2xx3^2xx7^4)#

#A=2xx3xx7^2#

#A=294#