GCSE Secondary Maths Age 13-17 - Pythagoras & Trigonometry: Trigonometry - Explained

The video tutorial explains how to solve a trigonometry problem involving a triangle with given angles and side lengths. It covers the use of the sine rule to find an unknown side in one triangle and the cosine rule to find another side in a different triangle. The tutorial emphasizes the importance of understanding when to use each rule and provides a step-by-step solution, including mark allocation for each part of the problem.

What is the first step in solving the problem involving the triangle ABC?

• Measure the angles using a protractor.

• Use the sine rule to find the length of BC.

• Identify the given angles and sides.

• Directly apply the cosine rule.

Which rule is used when you have two sides and the included angle in a triangle?

• Sine rule

• Area formula for triangles

• Cosine rule

• Pythagorean theorem

In the triangle BDC, what is the angle opposite to the side BC?

• 100 degrees

• 80 degrees

• 180 degrees

• 45 degrees

What is the calculated length of BD using the sine rule?

• 5.31 cm

• 7.4 cm

• 8.52 cm

• 5.8 cm

What is the final length of BC rounded to three significant figures?

• 8.53 cm

• 8.50 cm

• 8.51 cm

• 8.52 cm

Why is it important not to round off intermediate calculations?

• To make calculations easier

• To simplify the problem

• To save time

• To avoid losing accuracy

What is the key takeaway from solving this trigonometry problem?

• Always use the sine rule.

• Understand when to use sine and cosine rules.

• Measure angles accurately.

• Use only the cosine rule.