Answer:
Part 4) ![r=84\ units](https://tex.z-dn.net/?f=r%3D84%5C%20units)
Part 9) ![sin(\theta)=-\frac{\sqrt{5}}{3}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D-%5Cfrac%7B%5Csqrt%7B5%7D%7D%7B3%7D)
Part 10) ![sin(\theta)=-\frac{9\sqrt{202}}{202}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D-%5Cfrac%7B9%5Csqrt%7B202%7D%7D%7B202%7D)
Step-by-step explanation:
Part 4) A circle has an arc of length 56pi that is intercepted by a central angle of 120 degrees. What is the radius of the circle?
we know that
The circumference of a circle subtends a central angle of 360 degrees
The circumference is equal to
![C=2\pi r](https://tex.z-dn.net/?f=C%3D2%5Cpi%20r)
using proportion
![\frac{2\pi r}{360^o}=\frac{56\pi}{120^o}](https://tex.z-dn.net/?f=%5Cfrac%7B2%5Cpi%20r%7D%7B360%5Eo%7D%3D%5Cfrac%7B56%5Cpi%7D%7B120%5Eo%7D)
simplify
![\frac{r}{180^o}=\frac{56}{120^o}](https://tex.z-dn.net/?f=%5Cfrac%7Br%7D%7B180%5Eo%7D%3D%5Cfrac%7B56%7D%7B120%5Eo%7D)
solve for r
![r=\frac{56}{120^o}(180^o)](https://tex.z-dn.net/?f=r%3D%5Cfrac%7B56%7D%7B120%5Eo%7D%28180%5Eo%29)
![r=84\ units](https://tex.z-dn.net/?f=r%3D84%5C%20units)
Part 9) Given cos(∅)=-2/3 and ∅ lies in Quadrant III. Find the exact value of sin(∅) in simplified form
Remember the trigonometric identity
![cos^2(\theta)+sin^2(\theta)=1](https://tex.z-dn.net/?f=cos%5E2%28%5Ctheta%29%2Bsin%5E2%28%5Ctheta%29%3D1)
we have
![cos(\theta)=-\frac{2}{3}](https://tex.z-dn.net/?f=cos%28%5Ctheta%29%3D-%5Cfrac%7B2%7D%7B3%7D)
substitute the given value
![(-\frac{2}{3})^2+sin^2(\theta)=1](https://tex.z-dn.net/?f=%28-%5Cfrac%7B2%7D%7B3%7D%29%5E2%2Bsin%5E2%28%5Ctheta%29%3D1)
![\frac{4}{9}+sin^2(\theta)=1](https://tex.z-dn.net/?f=%5Cfrac%7B4%7D%7B9%7D%2Bsin%5E2%28%5Ctheta%29%3D1)
![sin^2(\theta)=1-\frac{4}{9}](https://tex.z-dn.net/?f=sin%5E2%28%5Ctheta%29%3D1-%5Cfrac%7B4%7D%7B9%7D)
![sin^2(\theta)=\frac{5}{9}](https://tex.z-dn.net/?f=sin%5E2%28%5Ctheta%29%3D%5Cfrac%7B5%7D%7B9%7D)
square root both sides
![sin(\theta)=\pm\frac{\sqrt{5}}{3}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D%5Cpm%5Cfrac%7B%5Csqrt%7B5%7D%7D%7B3%7D)
we know that
If ∅ lies in Quadrant III
then
The value of sin(∅) is negative
![sin(\theta)=-\frac{\sqrt{5}}{3}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D-%5Cfrac%7B%5Csqrt%7B5%7D%7D%7B3%7D)
Part 10) The terminal side of ∅ passes through the point (11,-9). What is the exact value of sin(∅) in simplified form?
see the attached figure to better understand the problem
In the right triangle ABC of the figure
![sin(\theta)=\frac{BC}{AC}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D%5Cfrac%7BBC%7D%7BAC%7D)
Find the length side AC applying the Pythagorean Theorem
![AC^2=AB^2+BC^2](https://tex.z-dn.net/?f=AC%5E2%3DAB%5E2%2BBC%5E2)
substitute the given values
![AC^2=11^2+9^2](https://tex.z-dn.net/?f=AC%5E2%3D11%5E2%2B9%5E2)
![AC^2=202](https://tex.z-dn.net/?f=AC%5E2%3D202)
![AC=\sqrt{202}\ units](https://tex.z-dn.net/?f=AC%3D%5Csqrt%7B202%7D%5C%20units)
so
![sin(\theta)=\frac{9}{\sqrt{202}}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D%5Cfrac%7B9%7D%7B%5Csqrt%7B202%7D%7D)
simplify
![sin(\theta)=\frac{9\sqrt{202}}{202}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D%5Cfrac%7B9%5Csqrt%7B202%7D%7D%7B202%7D)
Remember that
The point (11,-9) lies in Quadrant IV
then
The value of sin(∅) is negative
therefore
![sin(\theta)=-\frac{9\sqrt{202}}{202}](https://tex.z-dn.net/?f=sin%28%5Ctheta%29%3D-%5Cfrac%7B9%5Csqrt%7B202%7D%7D%7B202%7D)