First, some housekeeping:
cos = 12/13 is incomplete; "cos" must have an argument (input).
cos x = 12/13 is fine; here "cos" has the argument (input) x.
Given that cos x = 12/13, find sin x. To do this, we'll need to find the length of the opposite side, given that the hypo length is 13 and the adj. side length is 12.
12^2 + opp^2 = 13^2, or opp^2 = 169-144 = 25.
Then the opp side could be either 5 or -5. Let's assume that it's +5, and that angle x is in the first quadrant.
Then sin x = opp / hyp = 5/13 (answer)
cos 2 is an entirely different kind of problem. Here you are told what the argument (input) to the cosine function is (it is 2, which here means 2 radians).
Using a calculator: cos 2 = -0.416. Note that the angle 2 rad is in QII, which is why the "adjacent side" is negative and also why the cos of 2 is negative.
Answer:
Part A; Initial dosage is 10 milligrams
Part B:
8.4113 milligrams after 1 hour
5.0057 milligrams after 4 hours.
Step-by-step explanation:
It is given M(h)= 10 
Initial dosage is the 10 milligrams
After 1 hour, plug in h as 1
So, M(1)=10
Simplify the right side
M(1)=10(0.84113)
M(1)= 8.4113 milligrams.
Now, after 4 hours
M(4)=10 
M(4)=10(0.50057)
M(4) =5.0057 milligrams
I found that the given prices are $ 4 per pack of pens and $ 3 per pack of penciles.
The question is how much the bookstore spent on pens.
Then you have to multiply the number packs of pens, which is 1,528, times the price per pack pens which is $ 4.
So, the answer is: 1528 packs of pens * $ 4 / pack of pens = $6112.
