yammiled25san yammiled25san
  • 30-08-2021
  • Mathematics
contestada

In triangle ABC, a = 3, b = 5, and c = 7. Find the approximate value of angle A.

22°
38°
142°
158°

Respuesta :

sqdancefan
sqdancefan sqdancefan
  • 31-08-2021

9514 1404 393

Answer:

  a)  22°

Step-by-step explanation:

Side 'a' is the shortest side, so angle A will be the smallest angle. Its value must be less than 60°, eliminating the last two answer choices. The actual value can be found from the Law of Cosines.

  a² = b² +c² -2bc·cos(A)

  cos(A) = (b² +c² -a²)/(2bc) = (5² +7² -3²)/(2(5)(7)) = 65/70

  A = arccos(65/70) ≈ 21.7868°

Angle A is about 22°.

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