Answer:
[tex]\cos(\theta)= \frac{\sqrt{377}}{29}[/tex]
Step-by-step explanation:
Given
[tex]\sin(\theta) = -\frac{4}{\sqrt{29}}[/tex] -- the correct expression
Required
[tex]\cos(\theta)[/tex]
We know that:
[tex]\sin^2(\theta) + \cos^2(\theta)= 1[/tex]
Make [tex]\cos^2(\theta)[/tex] the subject
[tex]\cos^2(\theta)= 1 - \sin^2(\theta)[/tex]
Substitute: [tex]\sin(\theta) = -\frac{4}{\sqrt{29}}[/tex]
[tex]\cos^2(\theta)= 1 - (-\frac{4}{\sqrt{29}})^2[/tex]
Evaluate all squares
[tex]\cos^2(\theta)= 1 - (\frac{16}{29})[/tex]
Take LCM
[tex]\cos^2(\theta)= \frac{29 - 16}{29}[/tex]
[tex]\cos^2(\theta)= \frac{13}{29}[/tex]
Take square roots of both sides
[tex]\cos(\theta)= \±\sqrt{\frac{13}{29}}[/tex]
cosine is positive in the 4th quadrant;
So:
[tex]\cos(\theta)= \sqrt{\frac{13}{29}}[/tex]
Split
[tex]\cos(\theta)= \frac{\sqrt{13}}{\sqrt{29}}[/tex]
Rationalize
[tex]\cos(\theta)= \frac{\sqrt{13}}{\sqrt{29}} * \frac{\sqrt{29}}{\sqrt{29}}[/tex]
[tex]\cos(\theta)= \frac{\sqrt{13*29}}{29}[/tex]
[tex]\cos(\theta)= \frac{\sqrt{377}}{29}[/tex]
