Given:
cos 120°
To find:
The exact value of cos 120° in simplest form with a rational denominator.
Solution:
We have,

It can be written as

![[\because \cos (90^\circ-\theta)=-\sin \theta]](https://tex.z-dn.net/?f=%5B%5Cbecause%20%5Ccos%20%2890%5E%5Ccirc-%5Ctheta%29%3D-%5Csin%20%5Ctheta%5D)
![[\because \sin 30^\circ=\dfrac{1}{2}]](https://tex.z-dn.net/?f=%5B%5Cbecause%20%5Csin%2030%5E%5Ccirc%3D%5Cdfrac%7B1%7D%7B2%7D%5D)

Therefore, the exact value of cos 120° is
.
The answer would be 17n+6.
Rounded to the nearest hundred would be 274,389,451,400
2x+8+6=22
2x+14-14=22-14
2x = 8
2x/2 = 8/2
x = 4
Check your work
2(4+4)+6=22
2(8)+6=22
16+6=22
22=22
its giving me 50 points just for answering this so I'm happy