Electrical mathQuestion 149 of 1506

An isosceles triangle has a top angle of 40°. How large is each of the two equal base angles?

  1. 70°
  2. 40°
  3. 140°
  4. 80°
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Correct answer: 70°

The other two angles are equal and all three add to 180°, so each is (180° − 40°) ÷ 2 = 70°.

Source: Trigonometry and Single Phase AC Generation for Electricians (Flinn), 1.2: Triangles

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Questions last reviewed: 18 October 2026