
bearing in mind, "t" is in years, 6months is just 1/2 year
solve for "r", you'd get a decimal amount, multiply times 100, to get the percentage form
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 D. 18/6. We can figure this out because in the question, it says that each shape is worth one whole. There are three shapes so that means when added, the sum is 3 and 18/6, when reduced is 3.
I hope this helped! :-)