Pythagoras and Trigonometry: The Sine and Cosine Rules

The video tutorial explains how to find the largest angle in a triangle with sides of 8 cm, 10 cm, and 14 cm using trigonometry. It involves sketching the triangle, identifying the largest angle opposite the longest side, and applying the cosine rule. The tutorial details substituting side lengths into the formula, calculating the cosine of the angle, and using the inverse cosine function to find the angle, which is approximately 101.5 degrees. The video concludes with a recap and explanation of the marks allocation for the problem.

What is the largest angle in a triangle typically opposite to?

• The shortest side

• The longest side

• The side with the smallest angle

• The side with the largest angle

Which trigonometric rule is used when you have all three sides of a triangle but no angles?

• Pythagorean Theorem

• Cosine Rule

• Tangent Rule

• Sine Rule

In the cosine rule, what does the capital 'A' represent?

• The perimeter of the triangle

• The angle opposite side a

• The length of side a

• The area of the triangle

What is the formula for cosA in terms of sides a, b, and c?

• (b^2 + a^2 - c^2) / (2ab)

• (b^2 + c^2 - a^2) / (2bc)

• (a^2 + b^2 - c^2) / (2ab)

• (a^2 + c^2 - b^2) / (2ac)

What is the value of cosA when the sides are substituted into the formula?

• 0.2

• -0.2

• 1.2

• -1.2

What function is used to find the angle from the cosine value?

• Inverse cosine

• Inverse secant

• Inverse tangent

• Inverse sine

What is the final angle of the triangle rounded to one decimal place?

• 103.5 degrees

• 102.5 degrees

• 100.5 degrees

• 101.5 degrees