Search results
The law of sines works only if you know an angle, a side opposite it, and some other piece of information. If you know two sides and the angle between them, the law of sines won't help you. In any other case, you need the law of cosines.
the Law of Cosines (also called the Cosine Rule) says: c 2 = a 2 + b 2 − 2ab cos(C) It helps us solve some triangles. Let's see how to use it.
Law of sines defines the ratio of sides of a triangle and their respective sine angles are equivalent to each other. The other names of the law of sines are sine law, sine rule and sine formula. The law of sine is used to find the unknown angle or the side of an oblique triangle.
Tutorial on the law of sines and cosines and on how to decide which formula to use in triangle problems.
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 given by: c2 = a2 + b2 – 2ab cosγ.
The Law of Sines (or Sine Rule) is very useful for solving triangles: a sin A = b sin B = c sin C. It works for any triangle: a, b and c are sides. A, B and C are angles.
Theorem 2.2.1: Law of Cosines. If a triangle has sides of lengths a, b, and c opposite the angles A, B, and C, respectively, then. a2 = b2 + c2 − 2bc cos A , b2 = c2 + a2 − 2ca cos B , c2 = a2 + b2 − 2ab cos C .
