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Subject:  Trigonometry

Law of cosines: a = 7, b = 10, C = 60°

Use the law of cosines to find the third side and the remaining two angles.

Answer c = 8.88819, A = 43.0039°, B = 76.9961°

Solution

  1. Given a = 7, b = 10, included angle C = 60°
  2. Third side c² = a² + b² − 2ab·cos C = 149 − 70 → c = 8.88819
  3. Angle A cos A = (b² + c² − a²)/(2bc) → A = 43.0039°
  4. Angle B B = 180° − C − A = 76.9961°

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