How to use law of cosines to find the missing angles of a triangle given SSS

The video tutorial explains how to find missing angles in a triangle when only side lengths are given. It begins by discussing why the law of sines cannot be used due to the lack of angle information and introduces the law of cosines as a solution. The tutorial provides a detailed walkthrough of calculating the largest angle first using the law of cosines, followed by using the law of sines to find the remaining angles. The importance of identifying the largest angle first is emphasized to ensure the other angles are acute, simplifying the process.

Why can't the law of sines be used initially in this problem?

• Because the triangle is equilateral.

• Because the side lengths are not proportional.

• Because the triangle is not a right triangle.

• Because no angles are given.

What is the first step in using the law of cosines for this problem?

• Find the smallest angle.

• Find the largest angle.

• Find the angle opposite the smallest side.

• Find any angle.

Which angle is calculated first using the law of cosines?

• Angle B

• Any angle

• Angle A

• Angle C

What is the value of angle C after calculation?

• 122.88 degrees

• 45 degrees

• 60 degrees

• 90 degrees

Why is it important to find the largest angle first?

• To avoid using the law of sines.

• To ensure the other angles are obtuse.

• To ensure the other angles are acute.

• To simplify the calculation of side lengths.

How is angle A calculated after finding angle C?

• Using the law of sines.

• Using the triangle angle sum theorem.

• Using the law of cosines again.

• Using the Pythagorean theorem.

What theorem is used to find the final angle B?

• Triangle angle sum theorem

• Pythagorean theorem

• Law of cosines

• Law of sines