He would want to charge $0.85 per glass of lemonade to cover his expenses and have $10.00 profit. But in reality he would'nt make $17.00 because people don't carry freaking nickels and dimes.
Euler's formula tells us that


Suppose we subtract the two. This eliminates the cosine terms.

Divide both sides by

and you're done.
Answer: $1800
The theater income will be the total of audience multiplied by the ticket cost. To answer this question, you need to determine the total audience count. Assuming all the seats are occupied then:
Total audience= row of seats x seats/ row = 20x18 people = 360 people
After that the income would be:
Income = audience x ticket cost
Income= 360 people x $5 / people= $1800
The expressions is undefined in the set of the real numbers.