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Geometry and TrigonometryEasyVertex angle of an isosceles triangle

Geometry and Trigonometry practice question

In an isosceles triangle, the two equal base angles each measure 70°. What is the measure of the third angle?

  1. A. 40°Correct
  2. B. 70°
  3. C. 110°
  4. D. 20°

Answer: A. 40°

180 − 70 − 70 = 40.

Why the other answers are wrong

B. 70°
70° would make all three angles 70°, summing to 210.
C. 110°
110° is 180 − 70, subtracting only one base angle.
D. 20°
20° is half of 40; the third angle is the full remainder.

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