Answer: Sine rule.
- A Cosine rule
- B Sine rule
- C Area formula
- D Tangent rule
Correct answer: B. Sine rule
Explanation: This is the Sine Rule (Law of Sines): a/sinA=b/sinB=c/sinC=2R, where R is the circumradius. It connects each side to the sine of its opposite angle. Used to solve triangles when two angles and a side are known.
Unit circle with standard angles 0, 30, 45, 60, 90 degrees; at 45 degrees the point is (cos45, sin45) = (1/sqrt2, 1/sqrt2).
Concept context
Ratios, identities, and applications in triangles