SOLUTION: if the vertex of an isosceles triangle is 80 degrees and the side opposite the vertex measures 12 cm, determine the perimeter of the triangle.

Question 924424: if the vertex of an isosceles triangle is 80 degrees and the side opposite the vertex measures 12 cm, determine the perimeter of the triangle.

Found 2 solutions by Fombitz, MathLover1:
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Make two right triangles from the isosceles triangle by bisecting the vertex angle. The angle is then 40 degrees and the opposite side is 6 cm.

The perimeter is then,

Answer by MathLover1(20850) (Show Source): You can put this solution on YOUR website!
you can solve it this way:
An isosceles triangle can be considered as two right angle triangles joined together so use the tangent ratio to find its altitude :

given angle => angle
base
(where is the altitude and is half the base)

now we can find using Pythagorean theorem:

(triangle is isosceles, )

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