# Can you use law of cosines with SSS?

## Can you use law of cosines with SSS?

When you know the values for two or more sides of a triangle, you can use the law of cosines. In the following case, you know all three sides (which is called SSS, or side-side-side, in trigonometry) but none of the angles.

## What 3 formulas do we use for the law of cosines?

It can be in either of these forms:

• cos(C) = a2 + b2 − c2 2ab.
• cos(A) = b2 + c2 − a2 2bc.
• cos(B) = c2 + a2 − b2 2ca.

How do you find the law of cosines?

The Law of Cosines states: c2=a2+b2−2ab cosC . This resembles the Pythagorean Theorem except for the third term and if C is a right angle the third term equals 0 because the cosine of 90° is 0 and we get the Pythagorean Theorem.

### Is SAS law of cosines?

“SAS” is when we know two sides and the angle between them. use The Law of Cosines to calculate the unknown side, then use The Law of Sines to find the smaller of the other two angles, and then use the three angles add to 180° to find the last angle.

### Can you use SSS with the Law of Sines?

To solve a triangle means to find all the angles and all the side lengths. The Law of Sines is a valuable tool in solving triangles, but it requires knowing an angle and its opposite side. So, the Law of Sines can’t be used as a first step in solving SSS (side-side-side) or SAS (side-angle-side) configurations.

Is SAS Law of Cosines?

#### When can you use sine law?

This law is useful for finding a missing angle when given an angle and two sides, or for finding a missing side when given two angles and one side.

#### Why does the law of cosine work?

The cosine rule, also known as the law of cosines, relates all 3 sides of a triangle with an angle of a triangle. It is most useful for solving for missing information in a triangle. For example, if all three sides of the triangle are known, the cosine rule allows one to find any of the angle measures.

What is cosine law physics?

a law stating that the square of a side of a plane triangle is equal to the sum of the squares of the other two sides minus twice the product of the other sides multiplied by the cosine of the angle between them.

## When to use law of sines vs law of cosines?

You use the law of cosines to relate the 3 sides of a triangle to one of the angles. So if you are given the 3 sides you can find the angle; or if you are given two sides and the included angle (the angle between the two sides) you can find the side opposite the included angle. The law of sines relates the angles and the sides opposite them.

## What is the formula for cosine rule?

The Law of Cosines (also called the Cosine Rule) says:. c 2 = a 2 + b 2 − 2ab cos(C). It helps us solve some triangles. Let’s see how to use it.

What is a cosine law?

What is the Law of Cosines? The law of cosines also referred to as the cosine rule, is a formula that relates the three side lengths of a triangle to the cosine. We can use the cosine rule to find the three unknown angles of a triangle if the three side lengths of the given triangle are known.

### When to use the law of sines?

The law of sines is generally used to find the unknown angle or side of a triangle. This law can be used if certain combinations of measurement of a triangle are given. ASA Criteria: Given two angles and included side, to find the unknown side. AAS Criteria: Given two angles and a non-included side, to find the unknown side.