The sine of each angle should be proportional to the length of the opposite side of that triangle.

• A. Law of Sines
• B. Cosine Rule
• C. Side Condition
• D. Angle Subtension

Answer: (C)

This tests the relationship between a triangle’s sides and the sines of its opposite angles. In any triangle, each side is proportional to the sine of its opposite angle, so a : b : c = sin A : sin B : sin C. Equivalently, sin A / a = sin B / b = sin C / c, with the common factor being 1/(2R), where R is the circumradius (a = 2R sin A, etc.). This precise link is known as the Law of Sines, and it’s what lets you solve triangles when you know angles and sides in various combinations.

The other terms aren’t describing this fundamental relationship. The Cosine Rule involves squares of sides and cosines of an angle, not a direct sine-to-opposite-side proportionality. “Side Condition” and “Angle Subtension” aren’t standard names for this proportionality and don’t capture the same essential relation.