Law of Cosines The Law of Cosines, also called Cosine Rule or Cosine Law , states that the square of a side of a triangle is equal to the sum of the squares of the other two sides minus twice their product times the cosine of their included angle. Learn the cosine rule ( law of cosines) with simple formulas, step-by-step examples, and clear explanations for solving triangles. Includes angle, side, proof, and real-life applications. In trigonometry, the Cosine Rule says that the square of the length of any side of a given triangle is equal to the sum of the squares of the length of the other sides minus twice the product of the other two sides multiplied by the cosine of angle included between them. Cosine rule is also called law of cosines or Cosine Formula . Suppose, a, b and c are lengths of the side of a triangle ABC, then; Law of Cosines Definition In Trigonometry, the law of Cosines , also known as Cosine Rule or Cosine Formula basically relates the length of the triangle to the cosines of one of its angles. It states that, if the length of two sides and the angle between them is known for a triangle, then we can determine the length of the third side. It is ...
