Answer:
The equivalent trigonometric ratio in Quadrant I is [tex]-\cos (\frac{3\pi}{8})[/tex]
Step-by-step explanation:
The terminal side of [tex]\frac{27\pi}{8}[/tex] is in the 3rd quadrant.
The principal angle is [tex]\frac{3\pi}{8}[/tex]
In other words, the terminal side of [tex]\frac{27\pi}{8}[/tex] makes an acute angle of [tex]\frac{3\pi}{8}[/tex] radian with the positive x-axis. Acute angles are in the first quadrant.
Since the cosine ratio is negative in the 3rd quadrant,
[tex]\cos (\frac{27\pi}{8})=-\cos (\frac{3\pi}{8})[/tex]
