- #1

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## Homework Statement

Find the minimum and maximum values of x and the values of f(x) at these points if:

f(x) = 10.9sin(0.7x)+2.1cos(0.7x)

The range is (-.27,8.7)

## Homework Equations

I don't know/think there are any

## The Attempt at a Solution

I found f'(x) = 7.43cos(0.7x)-1.47sin(0.7x) = 0 and simplified to tan(0.7x) = 7.43/1.47. so arctan(7.43/1.47) = 0.7x or so I thought, but that doesn't seem to be the case as I can't find a value of x within the range.

Please give me some kind of advice, any help is welcome, thank you in advance.