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# 2015 AP Calculus AB/BC 1ab

Water in a pipe.

## Want to join the conversation?

• at , you calculated the answer in radians. Why did you use radians and how do you know when to use radians or degrees?
• When in doubt, assume radians. Almost all mathematicians use radians by default.

You can tell the difference between radians and degrees by looking for the `°` symbol. If the numbers of an angle measure are followed by a `°`, it will be degrees. Otherwise it will always be radians.

I hope this helps!
• In part one, wouldn't you need to account for the water blockage not letting water flow into the top because its already full?
• The blockage is already accounted for as it affects the rate at which it flows out. It does not specifically say that the top is blocked, it just says its blocked somewhere. That blockage just affects the rate the water comes out. That is why there are 2 different equations, I'm assuming the blockage is somewhere inside the pipe.
• What about the initial 30 cubic feet of water when t = 0 ?
• In part A, why didn't you add the initial variable of 30 to your final answer?
(1 vote)
• its not asking for total amount, just how much flowed in
• For part b, since the d(t) and r(t) indicates the rate of flow, why can't we just calc r(3) - d(3) to see the whether the answer is positive or negative?
(1 vote)
• Would it be possible to find the definite integral in part(a) by hand? If so what would it be?
(1 vote)
• Is there a way to merge these two different functions into one single function?
(1 vote)
• Can someone help me out with this question: Suppose that a function f(x) satisfies the relation (x^2+1)f(x) + f(x)^3 = 3 for every real number x. Evaluate f'(1) .
i would really be grateful if someone could post a solution to this question.
i'm quite confused
(1 vote)
• How do you know when to put your calculator on radian mode?
(1 vote)
• Usually for AP calculus classes you can assume that your calculator needs to be in radian mode unless otherwise stated or if all of the angle measurements are in degrees. I don't think I can recall a time when I was asked to use degree mode in calc class, except for maybe with some problems involving finding lengths of sides using tangent, cosines and sine. I hope this helped!
(1 vote)
• The result of question a should be 76.57 cubic feet. Sorry for nitpicking but stating what is the unit is very important.