The vertex angle of an isosceles triangle measures 40°. what is the measure of a base angle? 40° 70° 100° 140°

Answer

70°

Explanation

An isosceles triangle is a triangle with two equal sides. When two sides are equal, two of its angles will be also equal. This are the base angles of the triangle.

Let one of the base angle = x

Vertex angle is given a 40°.

Angles in a triangle add up to 180°

∴ 180 = 40 + x + x

 180 = 40 + 2x

  2x = 180 - 40

        = 140°

x = 140/2

    = 70°

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