Respuesta :

sqdancefan

Answer:

  ∠F ≈ 43.9°

Step-by-step explanation:

The Law of Cosines is used to find an angle when all triangle sides are known.

  f² = d² +e² -2de·cos(F)

  cos(F) = (d² +e² -f²)/(2de) = (25² +28² -20²)/(2·25·28) = 1009/1400

  F = arccos(1009/1400)

  F ≈ 43.9°