Which of the trigonometric expressions represent an inverse function?

Need this asap if anyone can i would be very grateful. if you could show workings that would really

Dakota earned $7.50 in interest in account a and $18.75 in interest in account b after 15 months. if the simple interest rate is 4% for account a and 5% for account b, which account has the greater principal? explain. to make it a little easier, there is an image. good luck!

What is the slope of the line shown below?