Answer:
[tex]\text{C. }\cos R=21/29[/tex]
Step-by-step explanation:
In any right triangle, the cosine of an angle is equal to its adjacent side divided by the hypotenuse.
From the diagram, we know:
- Angle R's adjacent side is 21
- The hypotenuse (longest side) of the right triangle is 29
Therefore, the cosine of angle R must be [tex]\boxed{\frac{21}{29}}[/tex]
