jakeharris02  Nov 4, 2017

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. 

supermanaccz  Nov 4, 2017

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  =


60 cm^2



cool cool cool

CPhill  Nov 4, 2017
edited by CPhill  Nov 4, 2017

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