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We use the law of Cosines to be able to find :

1. The measure of the third side, when the measure of two sides and the included angle of a triangle ABC are known.

2. The measure of any angle, when the measure of the three sides of a triangle ABC are known.

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Q: When do you use the Law of Cosines?
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Related questions

When would you use the law of sines or law of cosines instead of a trigonometric ratio?

Trigonometric ratios, by themselves, can only be used for right angled triangles. The law of cosines or the sine law can be used for any triangle.

Who discovered the law of cosines?

A caveman from 10,000 BCal-Kashi was the 1st to provide an explicit statement of the law of cosines in a form suitable for triangulation

How do you figure out the area of a triangle when you only know the sides?

Use the law of cosines (look them up on wikipedia).

Can you use the Law of Cosines to solve a triangle when you are given two side lengths and the included angle measure?

Yes, absolutely

What situation would you be FORCED to use law of cosines as opposed to law of sines?

When none of the angles are known, and using Pythagoras, the triangle is known not to be right angled.

How do you calculate the angles of a triangle knowing the sides?

Law of cosines

How do you find a missing side of a triangle without a right angle?

Having sufficient angles or sides one can use either, The Law of Sines, or, The Law of Cosines. Google them.

Is this statement true or falseYou can use the Law of Cosines to solve a triangle when you are given the lengths of the three sides and no angle measures?


Law of cosines with a right angle?

The law of cosines with a right angle is just the pythagorean theorem. The cosine of 90 degrees is 0. That is why the hypotenuse squared is equal to the sum of both of the legs squared

What are the answers to law of cosines in A plus?

The law of cosines can be written in one form as: c2 = a2 + b2 - 2abCos C. Without 3 of the 4 variables being given, there is no way to answer this question.

When you have a right angle what does the law of cosines reduce to?

cosine = adjacent/hypotenuse

Can the law of cosines be applied to right and non-right triangles?