# Thread: Graffing sine and cosine functions?

1. ## Graffing sine and cosine functions?

Can anyone explain to me how to do this as I am confused?

Find the values of angle which each equation is true
1. cos= -1
The back of the book says the answer is pi+ 2pi(n)
Know I know the cos of pi which is 180 degrees is -1
But I am confused on how to get 2pi(n)

2. Sorry I spelled graphing wrong

3. 180 + 360 degrees is the same thing as 180 degrees (rotate a whole circle once)
so is 180 + 360n.

4. The books answer is correct $\pi\pm 2n\pi$

$\cos x =-1$ has repeated solutions given the nature of the function.

The $\pm 2n\pi$ part comes from the period of the function and where the solution repeats, do you know how to find the period?

5. No I am not sure how to find the period. Can you also show me how you would do sin angle=1?

6. Originally Posted by homeylova223
No I am not sure how to find the period. Can you also show me how you would do sin angle=1?
The period of $\sin bx$ and $\cos bx$ is $\frac{2\pi}{b}$

The solution for $\sin x = 1 \implies x = \frac{\pi}{2}$ Now what is the period?

7. The period is 2pi. I see know because it repeat itself every 2pi I was looking at a chart from my book and your example and I just noticed that. So in order to test my understanding would sin angle=1 be pi/2+pi(n)?

8. Take a look at the graph of cosx. That should help you.

y=cosx