Trig Graphing Questions: Given graph find the function

[captainnumber36]

How do I solve these?

https://imgur.com/a/NvzxFcS

 

[captainnumber36]

26, 27 and 30 and the ones I'm not sure on. If you click on the link, you will find question 30.

 

[captainnumber36]

What I know is, Cos (x) is the X-axis and Sin (x) is the Y-axis. I also know the X stands for the degrees and that the value of sin or cos (x) is the value on the unit circle for that degree.

 

[captainnumber36]

I think I figured out 26. Since I know it's a Cos graph by the way it looks and since I know the amplitude of the Cos (X) is .5, that's how I know A. is correct.

For 27, I know the Y axis = 0 at 0, 180 and 360 degrees. This translates to the radian values and I do the math and find my answer to be five. (More explanation would be nice on this).

For 30, I think I just need to look at those kinds of graphs so I know what they look like.

 

[skeeter]

26. correct

27. period of $y=\sin(2x)$ is $\pi$ ... five zeros on the given interval is correct $\bigg\{0,\dfrac{\pi}{2}, \pi , \dfrac{3\pi}{2}, 2\pi \bigg\}$

30. The graph is $y=\ln{x}$ reflected over the x-axis, making it $y=-\ln{x}$

 

[captainnumber36]

26. correct

27. period of $y=\sin(2x)$ is $\pi$ ... five zeros on the given interval is correct $\bigg\{0,\dfrac{\pi}{2}, \pi , \dfrac{3\pi}{2}, 2\pi \bigg\}$
30. The graph is $y=\ln{x}$ reflected over the x-axis, making it $y=-\ln{x}$

Thanks!