In triangle ABC, a = 7, A = 30° and B = 45°. Using the sine rule, b equals

解說

b = 7 × sin 45° / sin 30° = 7 × (√2/2) / (1/2) = 7√2. The value 7√2/2 forgets the division by sin 30°. The value 14 is 7 / sin 30°.