If there are 250 bricks in a 20 feet high wall, there should be 125 bricks in a 10 feet high wall.
So to get a 30 feet high wall, you need to multiple 125 bricks by 3.
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
.
Answer: 183.27
Step-by-step explanation: look @ picture
The answer should be 3x^3 - x^2 - 5x + 3.