The Formula for the Law of Sines
The Law of Sines is used to Solve a Triangle. It can be used for any type of triangle.
Unlike SIN, COS, and TAN, that can only be applied to a Right Triangle, the Law of Sines is what you would want to use to Solve for the side lengths and angle measures of any triangle:
The Formula for the Law of Sines
When using the formula, you will only use 2 out of the 3 fractions. The two you pick depends on the information you are given.
As with all proportions (two fractions that are equal), fill in three of the four values and cross-multiply to get your answer.
Below are the three proportions you can chose from to Solve your triangle:
In the formula, capitalized variables represent the angle measures in degrees, and lower-case letters represent the side lengths of the triangle.
Enter each value given in your problem. Then click on the Submit button for the solution.
Example of entering your values: you must pair up the side length and the angle opposite of it when entering your values. So the side length 13 is opposite of the 70° angle. The side length of 10 is paired up with the angle C, the unknown value.
Example 2:
Enter the values for your triangle then hit submit for the solution. You can re-use the calculator below for each problem.
Side Length #1 =
Side Length #2 =
Angle #1 =
Angle #2 =