Determine Triangle Types

CONCEPTS

Tips

• 2 side length must be greater than 3rd side to make a triangle

Determine triangle type using the Pythagorean Theorem

• a² + b² = c² => right triangle

• a² + b² > c² => obtuse triangle

• a² + b² < c² => acute triangle

PRACTICE PROBLEMS

Question 1 Which angles could make up and obtuse triangle…1) 30°, 60°, 90° or 2) 80°, 40°, 60° or 3) 91°, 44°, 45°?

-- Answer --

(3, 4, 4) - not a triangle

(3, 4, 5) - right triangle 3² + 4² = 5²

(5, 12, 13) - right triangle 5² + 12² = 13²

(6, 8, 9) - acute triangle 6² + 8² = 100, 3rd side = 10 > 9

(6, 9, 13) - obtuse triangle, 117 < 169

ACT PRACTICE PROBLEMS

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