Because it is an iscocoles triangle, we know two sides are 13 and one side is 10.
Using heron's fomula: http://www.mathwarehouse.com/geometry/triangles/area/herons-formula-triangle-area.php
The answer is 60.
Thanks, sm!!!!.... we could use Heron's here, but here's a slightly easier approach...IMHO...!!!
Draw an altitude of the triangle......and the altitude of an isosceles triangle will divide the base in half
So....we will have two right triangles
Looking at either of these.....they will have a hypotenuse of 13cm and one leg = 1/2 of the base = 5cm
And the other leg will be sqrt (13^2 - 5^2) = sqrt (144) = 12cm = the height (altitude) of the triangle
So....the area is
1 / 2 base * height =
5 cm * 12 cm =