Answer:
100/3
Step-by-step explanation:
Given:
There are given that the cos function:

Explanation:
To find the value, first, we need to use the half-angle formula:
So,
From the half-angle formula:

Then,
Since 105 degrees is the 2nd quadrant so cosine is negative
Then,
By the formula:

Then,
Put the value of cos210 degrees into the above function:
So,

Final answer:
Hence, the value of the cos(105) is shown below:
The order of operations is used to order numerical expressions
Make 37.5% into decimal form : Since it is being marked up, add 100% = 1.375
1.375 x 80
1.375
x 80
_________
0000
+11000
_________
110.000
80 marked up by 37.5% is 110.