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Explain the Law of Sines and Cosines.

User Gmatht
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The Law of Sines and the Law of Cosines are mathematical principles used in trigonometry to solve triangles. They help calculate the lengths of sides and measures of angles in triangles, particularly when not all the information is known.

1. Law of Sines:
The Law of Sines relates the ratios of the lengths of sides to the sines of their opposite angles in a triangle. It states that the ratio of the length of a side to the sine of its opposite angle is constant across all sides of a triangle. The formula is as follows:

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

Here, a, b, and c represent the lengths of the sides, while A, B, and C represent the measures of the opposite angles. This law is especially useful when you know the lengths of two sides and the measure of an angle, or when you know the lengths of two sides and the ratio of the sines of two angles.

2. Law of Cosines:
The Law of Cosines allows you to calculate the lengths of sides or measures of angles in a triangle when you have information about the lengths of sides and/or measures of angles. It relates the lengths of sides to the cosine of one of the angles. The formula can be stated in two different forms:

a² = b² + c² - 2bc * cos(A)
b² = a² + c² - 2ac * cos(B)
c² = a² + b² - 2ab * cos(C)

In these formulas, a, b, and c represent the lengths of the sides, and A, B, and C represent the measures of the angles. This law is useful when you know the lengths of three sides or when you know the lengths of two sides and the measure of the included angle.

Both the Law of Sines and the Law of Cosines are powerful tools in trigonometry that enable the determination of missing information in triangles, allowing for accurate calculations in various mathematical and real-world applications.
User Kushyar
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Answer:

The sine rule is used when we are given either a) two angles and one side, or b) two sides and a non-included angle. The cosine rule is used when we are given either a) three sides or b) two sides and the included angle. Study the triangle ABC shown below. Let B stands for the angle at B.

User Philwinkle
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