# Isosceles triangle 8

If the rate of the sides an isosceles triangle is 7:6:7, find the base angle correct to the nearest degree.

Correct result:

B =  65 °

#### Solution:

$a=7 \ \\ b=6 \ \\ \ \\ \cos B=b/2 : a \ \\ \ \\ B=\dfrac{ 180^\circ }{ \pi } \cdot \arccos (\dfrac{ b/2 }{ a } )=\dfrac{ 180^\circ }{ \pi } \cdot \arccos (\dfrac{ 6/2 }{ 7 } )=65 ^\circ =64^\circ 37'23"$

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