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https://vle.mathswatch.co.uk/images/questions/question809.png

jakeharris02  Nov 4, 2017
 #1
avatar+606 
+1

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
 #2
avatar+86859 
+1

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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