Question 87098
Use Hero's Formula:
s = perimeter / 2
where
{{{Area = sqrt(s(s - a)(s - b)(s - c))}}}
where
a, b, and c are sides
~
s = (12 + 13 + 15) / 2 = (40) / 2 = 20
{{{A = sqrt(s(s - a)(s - b)(s - c))}}}
{{{A = sqrt(20(20 - a)(20 - b)(20 - c))}}}
{{{A = sqrt(20(20 - 12)(20 - 13)(20 - 15))}}}
{{{A = sqrt(20(8)(7)(5))}}}
{{{A = sqrt((4)(5)(2)(4)(7)(5))}}}
{{{A = 5*sqrt((4)(2)(4)(7))}}}
{{{A = 10*sqrt((4)(2)(7))}}}
{{{A = 20*sqrt((2)(7))}}}
{{{A = 20*sqrt(14)}}}