A road sign at the top of a mountain indicates that for the next 4 miles the grade is 12%. Find the angle of the grade and the change in elevation for a car descending the mountain.

Find a problem like that in your notes and in your textbook. This seems to simple to ask for someone's help (where here you'll most likely get the answer without you actually understanding it).

If you're actually really stuck, explain what you've done so far and why you need help.

Calculus = Smart People

The answer is true

I'm really bad at word problems in calculus but I think you need to use tan theta to find the angle. Then after you find the angle, you'd need to find the change in elevation from which the car is descending so that means rate of change. dy/dx.

Since the sign is at the top of the mountain, it forms a triangle. You need to derive the Pythagorean theorem to find the rate of change of elevation. I'm sorry I couldn't be of more help.