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Learn how to use the law of sines and the law of cosines to solve problems with any triangle. See examples, practice sets, videos and tips on how to apply these laws.
- Law of cosines: solving for an angle - Khan Academy
If they give you 0 angles and 3 sides, then you have to use...
- Law of cosines: solving for an angle - Khan Academy
Law of Sines. Worksheet on law of sines and law of cosines (pdf) Tutorial on the law of sines and cosines and on how to decide which formula to use in triangle problems.
To find \(m\angle A\) or \(m\angle C\), you can use either the Law of Sines or Law of Cosines. Let’s use the Law of Sines. \(\begin{aligned} \dfrac{\sin 26^{\circ} }{12.60}&=\dfrac{\sin A}{18} \\ 12.60\cdot \sin A&=18\cdot \sin 26^{\circ} \\ \sin A&=18\cdot \sin 26^{\circ} 12.60 \end{aligned}\)
To find angles and distances on this imaginary sphere, astronomers invented techniques that are now part of spherical trigonometry. The laws of sines and cosines were first stated in this context, in a slightly different form than the laws for plane trigonometry.
Learn how to use the Law of Sines (or Sine Rule) to solve triangles with one angle and two sides known. See examples, formulas, diagrams and tips on how to avoid two possible answers.
Learn how to use the Law of Cosines 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 this trigonometry rule.
If they give you 0 angles and 3 sides, then you have to use law of cosines to find one of the angles. If they give you 1 angle and 2 sides and the given angle is opposite of one of the sides and the unknown angle is opposite of the other given side, then you can use law of sines.
