Question 418717
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Hi
isosceles triangle with sides having lengths 5(the base), 10, and 10
(picture dropping altitude down intersecting the base)
the Base Angles = 75.5°  cos &#952;= adj/hyp = 2.5/10 = .25  &#952; = 75.5°
The angle across from the base = 29°  (180°-151°)  
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Triangle.Isosceles.svg/200px-Triangle.Isosceles.svg.png">