1. If [tex]$0^{\circ} \ \textless \ \theta \ \textless \ 90^{\circ}$[/tex] and [tex]$\cos \theta = \frac{11}{61}$[/tex], find [tex][tex]$\cot \theta$[/tex][/tex] using trigonometric identities.

A. [tex]$\frac{11}{60}$[/tex]
B. [tex]$\frac{60}{11}$[/tex]
C. [tex][tex]$\frac{11}{61}$[/tex][/tex]
D. [tex]$\frac{61}{11}$[/tex]



Answer :

To find [tex]\(\cot \theta\)[/tex] given [tex]\(\cos \theta = \frac{11}{61}\)[/tex] for [tex]\(0^\circ < \theta < 90^\circ\)[/tex], follow these steps:

1. Understand the identity involving sine and cosine:

We know the Pythagorean identity for trigonometric functions:
[tex]\[ \cos^2 \theta + \sin^2 \theta = 1 \][/tex]

2. Substitute [tex]\(\cos \theta\)[/tex] into the identity:

Given [tex]\(\cos \theta = \frac{11}{61}\)[/tex], we square this value to find [tex]\(\cos^2 \theta\)[/tex]:
[tex]\[ \cos^2 \theta = \left(\frac{11}{61}\right)^2 = \frac{121}{3721} \][/tex]

3. Solve for [tex]\(\sin^2 \theta\)[/tex]:

Using the identity [tex]\(\cos^2 \theta + \sin^2 \theta = 1\)[/tex]:
[tex]\[ \sin^2 \theta = 1 - \cos^2 \theta = 1 - \frac{121}{3721} = \frac{3721 - 121}{3721} = \frac{3600}{3721} \][/tex]

4. Calculate [tex]\(\sin \theta\)[/tex]:

Since we are considering [tex]\(0^\circ < \theta < 90^\circ\)[/tex], [tex]\(\sin \theta\)[/tex] must be positive:
[tex]\[ \sin \theta = \sqrt{\frac{3600}{3721}} = \frac{60}{61} \][/tex]

5. Use the definition of [tex]\(\cot \theta\)[/tex]:

We know that [tex]\(\cot \theta = \frac{\cos \theta}{\sin \theta}\)[/tex]. Substitute the values we found for [tex]\(\cos \theta\)[/tex] and [tex]\(\sin \theta\)[/tex]:
[tex]\[ \cot \theta = \frac{\cos \theta}{\sin \theta} = \frac{\frac{11}{61}}{\frac{60}{61}} = \frac{11}{60} \][/tex]

Thus, the value of [tex]\(\cot \theta\)[/tex] is [tex]\(\boxed{\frac{11}{60}}\)[/tex].