In a right triangle [tex]\( XYZ \)[/tex], [tex]\(\angle X\)[/tex] and [tex]\(\angle Z\)[/tex] are complementary angles, and [tex]\(\cos(\angle X) = \frac{9}{11}\)[/tex]. What is [tex]\(\sin(\angle Z)\)[/tex]?

A. [tex]\(\frac{11}{9}\)[/tex]

B. [tex]\(\frac{\sqrt{20}}{11}\)[/tex]

C. [tex]\(\frac{\sqrt{20}}{9}\)[/tex]

D. [tex]\(\frac{9}{11}\)[/tex]



Answer :

To solve this problem, let's first recap some important trigonometric principles involving complementary angles. In a right triangle, the sum of the two non-right angles is [tex]\(90^\circ\)[/tex]. Two angles that sum to [tex]\(90^\circ\)[/tex] are called complementary angles.

Given:
- [tex]\(\angle X\)[/tex] and [tex]\(\angle Z\)[/tex] are complementary.
- [tex]\(\cos(X) = \frac{9}{11}\)[/tex].

Here's a step-by-step solution to find [tex]\(\sin(Z)\)[/tex]:

1. Understanding the Complementary Relationship:
- Since [tex]\(\angle X\)[/tex] and [tex]\(\angle Z\)[/tex] are complementary, we have:
[tex]\[ X + Z = 90^\circ \][/tex]
- The sine of an angle is equal to the cosine of its complementary angle:
[tex]\[ \sin(Z) = \cos(X) \][/tex]

2. Substitute the Given Value:
- We know [tex]\(\cos(X) = \frac{9}{11}\)[/tex].
- Therefore:
[tex]\[ \sin(Z) = \cos(X) = \frac{9}{11} \][/tex]

Thus, the value of [tex]\(\sin(Z)\)[/tex] is [tex]\(\frac{9}{11}\)[/tex].

Hence, the correct answer is:
[tex]\[ \boxed{\frac{9}{11}} \][/tex]

From the given choices, the correct option is D.