In the right triangle shown, angle B is a right angle. The length of side AB is 29. The length of side CA is 47. What is the value of cos A?

What is the value of cos A? | SAT Right triangles and trigonometry Practice

Answer: C) $\dfrac{29}{47}$

Context: Right triangle with right angle at $B$ . $AB = 29$ (adjacent to $A$ ), $CA = 47$ (hypotenuse).

Answer: $\cos A = \dfrac{\text{adjacent}}{\text{hypotenuse}} = \dfrac{AB}{CA} = \dfrac{29}{47}$ .

Why: Cosine = Adjacent / Hypotenuse. $AB = 29$ is adjacent to angle $A$ , $CA = 47$ is the hypotenuse.

Traps: A) $\dfrac{1}{47}$ , B) $\dfrac{1}{29}$ — no side equals $1$ . D) $\dfrac{47}{29}$ — greater than $1$ , impossible for cosine.