Understanding the Cosine Law

The video tutorial explains the cosine law, its applications, and provides examples. It starts by encouraging viewers to understand the sine law first. The first example demonstrates using the cosine law to find a side length when two sides and the included angle are known. The second example shows how to find an angle when all three sides of a triangle are known. The video concludes with a summary of when to use the cosine law.

What is recommended to watch before this video?

• The Sine Law video

• The Trigonometry Introduction video

• The Pythagorean Theorem video

• The Algebra Basics video

Why can't the Sine Law be used in the given triangle scenario?

• Because there are no angles given

• Because there are no opposite pairs of dimensions

• Because all sides are equal

• Because the triangle is not right-angled

What should be done if the Sine Law cannot be applied?

• Use the Law of Cotangents

• Use the Law of Tangents

• Use the Cosine Law

• Use the Pythagorean Theorem

What is the main purpose of the Cosine Law?

• To find the height of a triangle

• To find the area of a triangle

• To find the perimeter of a triangle

• To find a side or angle in a triangle

How many versions of the Cosine Law formula are there?

• One

• Two

• Three

• Four

In the example problem, what angle is used in the Cosine Law?

• 30°

• 45°

• 90°

• 67°

What is the approximate value of side 'a' found using the Cosine Law?

• 11.3

• 13.7

• 10.5

• 12.26

What is the result of simplifying the equation in the example problem?

• a^2 = 200

• a^2 = 144

• a^2 = 100

• a^2 = 115.22

What is the first step in using the Cosine Law to find a side?

• Plug in the angle opposite the side

• Add all angles together

• Multiply all sides

• Subtract the smallest side from the largest

What is the approximate value of cosine 67° used in the example?

• 0.6

• 0.39

• 0.4

• 0.5