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Learn how to use the cosine rule to find the third side or the angles of a triangle when you know two sides and the angle between them. See examples, formulas, and tips to remember the law of cosines.
- The Law of Sines
The Law of Sines (or Sine Rule) is very useful for solving...
- The Law of Sines
Learn how to use the cosine rule to find the lengths of the sides and angles of a triangle. The cosine rule is based on the law of cosines and the Pythagoras theorem. See the formula, proof and solved examples.
In trigonometry, the law of cosines (also known as the cosine formula or cosine rule) relates the lengths of the sides of a triangle to the cosine of one of its angles.
Learn the cosine rule, a formula that relates the sides and angles of a triangle. See the statement, proof, applications, and examples of using the cosine rule to solve problems.
Learn how to use the law of cosines to find the missing side or angle of a triangle given the known elements. The law of cosines relates the lengths of the sides of a triangle to the cosine of one of its angles and generalizes the Pythagoras theorem.
Learn how to use the law of cosines to solve triangles given two sides and an included angle or three sides. See examples, solutions, videos, proofs and applications of the cosine rule.
Jul 1, 2024 · Let a, b, and c be the lengths of the legs of a triangle opposite angles A, B, and C. Then the law of cosines states a^2 = b^2+c^2-2bccosA (1) b^2 = a^2+c^2-2accosB (2) c^2 = a^2+b^2-2abcosC. (3) Solving for the cosines yields the equivalent formulas cosA = (-a^2+b^2+c^2)/(2bc) (4) cosB = (a^2-b^2+c^2)/(2ac) (5) cosC = (a^2+b^2-c^2)/(2ab).
