SOLUTION: If each base angle of an isoceles triangle measures 55degrees,find the measure of the vertex angle of the triangle

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Question 32980This question is from textbook amsco's mathematics A
: If each base angle of an isoceles triangle measures 55degrees,find the measure of the vertex angle of the triangle This question is from textbook amsco's mathematics A

Answer by sarah_adam(201) About Me  (Show Source):
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One of Euclid's theorems is that the base angles of an isosceles triangle are congruent (equal). An isosceles triangle is a triangle in which two of the sides are conguent (equal). The base angles are the angles opposite the two congruent sides.
in triangle ABC if angle B and Angle C are base angles and Angle A is the vertex angle
so here angle B= ANgle C = 55degress
we know sum of angles in triangle are 180 degreess
therfore Angle A + Angle B +Angle C = 180 degrees
Angle A +55+55 = 180
Angle A = 180 - 110
Angle A = 70 degrees