- #1

- 16

- 0

i don't think the answer should be negative as the question is looking for a day of the year.

so if i try to solve for x, i end up with

-2.76 = cos [0.017x - 2.924]

-1.8876 = cos 0.017x

-1.8876/0.9999 = x

x = -1.8878

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- Thread starter phy_
- Start date

- #1

- 16

- 0

i don't think the answer should be negative as the question is looking for a day of the year.

so if i try to solve for x, i end up with

-2.76 = cos [0.017x - 2.924]

-1.8876 = cos 0.017x

-1.8876/0.9999 = x

x = -1.8878

- #2

Mentallic

Homework Helper

- 3,798

- 94

Reason is that the cosine of a value ranges between -1 and 1.

[tex]A=Bcos\theta[/tex]

[tex]cos\theta=\frac{A}{B}[/tex]

Therefore, to have a real solution for [itex]\theta[/itex], [tex]-1\leq \frac{A}{B}\leq 1[/tex]

But in the case of your equation:

[tex]-10.5=3.8cos(\frac{2\pi (x-172)}{360})[/tex]

[tex]cos(\frac{2\pi (x-172)}{360})=\frac{-10.5}{3.8}[/tex]

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