Geometry & MeasuresStudy Notes

Worked Example: Finding a Side

Part of Sine RuleGCSE Mathematics

This study notes covers Worked Example: Finding a Side within Sine Rule for GCSE Mathematics. Revise Sine Rule in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 4 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 4 of 4

Practice

12 questions

Recall

3 flashcards

Worked Example: Finding a Side

In triangle ABC, A = 40°, B = 75°, and a = 8cm. Find b.

Solution

a/sin A = b/sin B

8/sin 40° = b/sin 75°

b = 8 × sin 75° / sin 40°

b = 8 × 0.966 / 0.643 = 12.0 cm (1 d.p.)

Keep building this topic

Read this section alongside the surrounding pages in Sine Rule. That gives you the full topic sequence instead of a single isolated revision point.

Practice Questions for Sine Rule

Which of the following is the sine rule?

  • A. a/sinA = b/sinB = c/sinC
  • B. a² = b² + c² − 2bc cosA
  • C. Area = ½ab sinC
  • D. sinA/a = sinB/b + sinC/c
1 markfoundation

Explain what is meant by the ambiguous case of the sine rule, and state when it can occur.

3 markshigher

Quick Recall Flashcards

Sine Rule
a/sin A = b/sin B = c/sin C
Sine Rule
a/sinA = b/sinB = c/sinC. Use when you have a matched pair (side with opposite angle).

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