Solve Secx=-5.2 | Find Solutions for x Between 0 and 2π

[dragon513]

Q. Solve: secx=-5.2
x is greater than or equal to zero and less than or equal to 2π

I got 1.76 and 4.52, but answer key only has 1.76.

Am I not right?

 

[opticaltempest]

I find the same answers as you do when I do a quick check using my TI-89. Hmmm

 

[VietDao29]

Q. Solve: secx=-5.2
x is greater than or equal to zero and less than or equal to 2π
I got 1.76 and 4.52, but answer key only has 1.76.
Am I not right?

Yup, that looks good to me. Your answer is correct!

 

[dragon513]

Thank you!

 

[Ouabache]

Thank you!

Once you had the first solution 1.76, how did you find the 2nd one?

 

[VietDao29]

Since you have cos(-x) = cos(x), and $\cos x = \cos (x + 2k \pi) \ \ , k \in \mathbb{Z}$
So the second one is just:
$$- 1.76 + 2 \pi = 4.52$$

 

[Ouabache]

Thanks for answering, but I was asking dragon513.
dragon513, what was your approach for finding the 2nd angle?