Solving Oblique Triangles with the Law of Cosines

This video tutorial teaches how to solve non-right triangles using the law of cosines. It begins with an introduction to the law of cosines and a review of other triangle-solving methods like the Pythagorean theorem and the law of sines. The video explains the law of cosines formula and its notation, followed by two cases: finding an angle when all sides are known and finding a side when two sides and an included angle are given. The tutorial concludes with a caution to use the correct trigonometric law for different cases.

Which of the following is NOT a method used to solve triangles as mentioned in the introduction?

• Trigonometric inverses

• Pythagorean theorem

• Law of sines

• Law of tangents

In the first case of the law of cosines, what is required to find an angle?

• Two sides and the included angle

• One angle and one side

• All three sides

• Two angles and one side

What is the approximate measure of angle Y when using the law of cosines with sides 14, 10, and 21?

• 60.0 degrees

• 50.2 degrees

• 34.8 degrees

• 45.0 degrees

In the second case of the law of cosines, what is the known angle used in the example?

• 90 degrees

• 81 degrees

• 60 degrees

• 45 degrees

What is the approximate length of side MN when using the law of cosines with sides 11, 8, and angle 81 degrees?

• 9.8 units

• 10.5 units

• 12.55 units

• 15.0 units