Question

Which of the following best corresponds to the x-value where the function f(x) = cosx is a minimum in the interval x=[25, 30]?

X
Ο Α. 25.1
O B. 26.7
OC. 28.3
OD. 29.8

Answer 1

C

Explanation:

Cos x has a minimum of -1.

So Let find what x value in radians will equal -1

`\cos(x) = - 1`

This occurs at x=pi

`\cos {}^( - 1) (1) = \pi`

Since cos is a periodic function, we add 2pi to it continously

`\pi + 2\pi n`

convert pi to 3.14

`3.14 + 2(3.14)n`

`3.14 + 6.28n`

Let try when n is 4

`3.14+(6.28)4`

`3.14 + 25.12`

`28.26`

`28.3`