According to the CAH mnemonic, how is cosine defined?

• A. Cosine = opposite/hypotenuse
• B. Cosine = adjacent/hypotenuse
• C. Cosine = hypotenuse/opposite
• D. Cosine = adjacent/opposite

Answer: (B)

In the context of the CAH mnemonic, cosine is defined as the ratio of the length of the adjacent side to the length of the hypotenuse in a right triangle. The mnemonic itself stands for "Cosine = Adjacent/Hypotenuse," helping to memorize the relationship between these sides.

In a right triangle, if you take one of the angles (other than the right angle), the side that is next to (or adjacent to) that angle is compared to the longest side of the triangle, which is the hypotenuse. This relationship is foundational in trigonometry and is crucial for solving various problems involving angles and lengths in triangles. By recalling this definition, students can effectively apply the concept of cosine in numerous mathematical and physical contexts.