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 5 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and 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.)
Practice questions for Sine Rule
Which of the following is the sine rule?
Explain what is meant by the ambiguous case of the sine rule, and state when it can occur.
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).