The measure of the base angle of an isosceles triangle is 58°.
"It is a triangle in which all three angles are less than 90°, and at least two of its angles are equal."
For given example,
The vertex angle of an isosceles triangle measures 64 degrees.
We know, for an isosceles triangle two base angles are of equal measures.
Let ∠x and ∠y are base angles of an isosceles triangle.
⇒ ∠x = ∠y
We know, the sum of all angles of the triangle is 180°.
⇒ ∠x + ∠y + 64 = 1 80
⇒ ∠x + ∠x = 180 - 64 .....................(Since, ∠x = ∠y)
⇒ 2(∠x) = 116
⇒ ∠x = 116/2
⇒ ∠x = 58°
⇒ ∠y = 58°
Therefore, the measure of the base angle of isosceles triangle is 58°.
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