Well... you don't necessarily need to get the cosine value, in order to get the double angle
Answer:
Step-by-step explanation:
Required polynomial

Answer:
(a)
(b)
(c)R'(5400)=$394
Step-by-step explanation:
Given that x is the quantity demanded and the speaker's unit price (in dollars) is p where:
p = −0.02x + 610 (0 ≤ x ≤ 20,000)
(a)Revenue function R.
Revenue = Price X Quantity Demanded
Therefore:
R(x)=xp

(b)Marginal revenue function R'(x)
If 
Then, the marginal revenue function

(c)We want to compute R'(5,400)

From the above, we can infer that the revenue that will be generated on the sales of the 5401st item is $394.
No,
one of the 3 sides need to be 90