# Law of Sines

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The law of sines is a mathematical formula that relates the lengths of the sides and the angles of a triangle. It states that the ratio of the length of a side of a triangle to the sine of the angle opposite that side is the same for all sides and angles in the triangle. This ratio is called the "sine ratio."

## You can write the law of sines in the following form:

a/sin A = b/sin B = c/sin C

where a, b, and c are the lengths of the sides of the triangle, and A, B, and C are the angles opposite those sides.

The law of sines can be used to find missing side lengths or angles in a triangle when you know the lengths of two sides and the angle between them, or when you know the lengths of all three sides. It is often used in trigonometry and geometry to solve problems involving triangles.

For example, suppose you have a triangle with sides of lengths a = 3, b = 4, and c = 5, and angles A, B, and C as shown in the diagram. Using the law of sines, you can find the measure of angle A like this:

sin A = (a/c) * sin C

= (3/5) * sin C

= 0.6 * sin C

You would need to use a calculator or a table of sines to find the value of sin C and then solve for A to find the measure of angle A.