Question Bank

Official NZQA past exam questions • AS91578 Differentiation

With video explanations by infinityplusone

15 questions
Achievement
Differentiate y=3x21y = \sqrt{3x^2 - 1}.

*You do not need to simplify your answer.*
Achievement
Find the rate of change of the function f(t)=5ln(3t1)f(t) = 5\ln(3t - 1) when t=4t = 4.

*You must use calculus and show any derivatives that you need to find when solving this problem.*
Find the gradient of the tangent to the curve y=e2x1+x2y = \dfrac{e^{2x}}{1+x^2} at the point where x=2x = 2.

*You must use calculus and show any derivatives that you need to find when solving this problem.*
For what value(s) of xx is the function y=x3exy = x^3 e^x decreasing?

You must use calculus and show any derivatives that you need to find when solving this
problem.
Excellence
The volume of a sphere is increasing.

At the instant when the sphere’s radius is 0.50.5 m, the surface area of the sphere is increasing at
a rate of 0.40.4 m2^2 s1^{-1}.

Find the rate at which the volume of the sphere is increasing at this instant.

*You must use calculus and show any derivatives that you need to find when solving this
problem.*
Achievement
Differentiate y=(2x5)4y = (2x - 5)^4.

*You do not need to simplify your answer.*
Achievement
Find the gradient of the tangent to the curve y=tan2xy = \tan 2x at the point on the curve where x=π6x = \dfrac{\pi}{6}.

You must use calculus and show any derivatives that you need to find when solving this
problem.
A curve is defined parametrically by the equations x=1(5t)2x = \dfrac{1}{(5-t)^2} and y=5tt2y = 5t - t^2.

Find the gradient of the tangent to the curve at the point when t=2t = 2.

*You must use calculus and show any derivatives that you need to find when solving this problem.*
The Wynyard Crossing bridge in Auckland can be raised and lowered to allow tall boats to
sail through when open, and pedestrians to walk across when closed. The bridge consists of
two arms, each of length 22 metres.

When the bridge is rising, the angle of the bridge arm above the horizontal increases at the
rate of 0.01 rad s10.01\ \mathrm{rad\ s^{-1}}.
Loading diagram...
Find the rate at which the height, BH, is increasing when H is 15 metres above the horizontal,
FB.

*You must use calculus and show any derivatives that you need to find when solving this
problem.*
Excellence
If y=euy = e^u and u=sin2xu = \sin 2x show that

d2ydx2=d2ydu2(dudx)2+dydud2udx2\dfrac{d^2 y}{dx^2} = \dfrac{d^2 y}{du^2}\left(\dfrac{du}{dx}\right)^2 + \dfrac{dy}{du}\cdot\dfrac{d^2 u}{dx^2}

*You must use calculus and show any derivatives that you need to find when solving this
problem.*
Achievement
Differentiate y=4sinxy = \dfrac{4}{\sin x}.

*You do not need to simplify your answer.*
Achievement
The graph below shows the function y=f(x)y = f(x).
Loading diagram...
(i) Find all the value(s) of xx which meet each of the following conditions:

1. f(x)=0f'(x) = 0:

2. f(x)f(x) is not differentiable:

(ii) What is the value of limx1f(x)\lim_{x \to 1} f(x)?

State clearly if the value does not exist.