Question

Express cos(27pi/8) as a trigonometric function of an angle in Quadrant I.

Answer 1

c on edgen

Explanation:

Answer 2

The equivalent trigonometric ratio in Quadrant I is
`-\cos ((3\pi)/(8))`

Explanation:

The terminal side of
`(27\pi)/(8)` is in the 3rd quadrant.

The principal angle is
`(3\pi)/(8)`

In other words, the terminal side of
`(27\pi)/(8)` makes an acute angle of
`(3\pi)/(8)` radian with the positive x-axis. Acute angles are in the first quadrant.

Since the cosine ratio is negative in the 3rd quadrant,

`\cos ((27\pi)/(8))=-\cos ((3\pi)/(8))`