Find dy/dx given that y = sin x / 1 + cos x​

Ineed me i stuck and i don’t want to get it wrong

Leslie started last week with $1200 in her checking account. during the week, she wrote the checks below.

Recall that the owner of a local health food store recently started a new ad campaign to attract more business and wants to know if average daily sales have increased. historically average daily sales were approximately $2,700. the upper bound of the 95% range of likely sample means for this one-sided test is approximately $2,843.44. if the owner took a random sample of forty-five days and found that daily average sales were now $2,984, what can she conclude at the 95% confidence level?