16Hit1600
Geometry and TrigonometryEasy–MediumClassifying a triangle from two angles

Geometry and Trigonometry practice question

Two angles of a triangle measure 40° and 75°. Which of the following describes the triangle?

  1. A. Acute, because all three angles are less than 90°Correct
  2. B. Obtuse, because the third angle is greater than 90°
  3. C. Right, because the third angle is 90°
  4. D. Equilateral, because all angles are equal

Answer: A. Acute, because all three angles are less than 90°

The third angle is 180 − 40 − 75 = 65, so all three are acute.

Why the other answers are wrong

B. Obtuse, because the third angle is greater than 90°
The third angle is 65, not more than 90.
C. Right, because the third angle is 90°
The third angle is 65, not 90.
D. Equilateral, because all angles are equal
The angles differ.

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