Question Bank

Official NZQA past exam questions • AS91578 Differentiation

With video explanations by infinityplusone

15 questions
Achievement
Differentiate y=1+x1x+1x2y = 1 + x - \frac{1}{x} + \frac{1}{x^2}.
Achievement
The height of the tide at a particular beach today is given by the function

h(t)=0.8sin(4π25t+π2)h(t) = 0.8\sin\left(\frac{4\pi}{25}t+\frac{\pi}{2}\right)

where hh is the height of water, in metres, relative to the mean sea level
and tt is the time in hours after midnight.
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At what rate was the height of the tide changing at that beach at 9.00 a.m. today?
A curve is defined by the parametric equations

x=2cos2tx = 2\cos 2t and y=tan2ty = \tan^2 t.

Find the gradient of the tangent to the curve at the point where t=π4t = \dfrac{\pi}{4}.

*You must use calculus and show any derivatives that you need to find when solving this problem.*
The tangents to the curve y=14(x2)2y = \frac{1}{4}(x - 2)^2 at points P and Q are perpendicular.
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Q is the point (6,4)(6, 4).

What is the xx-coordinate of point P?
*You must use calculus and show any derivatives that you need to find when solving this problem.*
Excellence
A curve is defined by the function f(x)=e(xk)2f(x)=e^{-(x-k)^2}.

Find, in terms of kk, the xx-coordinate(s) for which f(x)=0f''(x)=0.

*You must use calculus and show any derivatives that you need to find when solving this problem.*
Achievement
Differentiate f(x)=xln(3x1)f(x)=x\ln(3x-1).
Achievement
Find the gradient of the tangent to the function y=2x1y = \sqrt{2x - 1} at the point (5,3)(5, 3).

*You must use calculus and show any derivatives that you need to find when solving this problem.*
The graph below shows the function y=f(x)y = f(x).
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For the function y=f(x)y = f(x) above:

(i) Find the value(s) of xx that meet the following conditions:

1. ff is not continuous:

2. ff is not differentiable:

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

4. f(x)<0f''(x) < 0:

(ii) What is the value of limx1f(x)\lim_{x\to-1} f(x)?
State clearly if the value of the limit does not exist.
A large spherical helium balloon is being inflated at a constant rate of 48004800 cm3^3 s1^{-1}.

At what rate is the radius of the balloon increasing when the volume of the balloon is
288000π288\,000\pi cm3^3?

*You must use calculus and show any derivatives that you need to find when solving this
problem.*
Excellence
A cone of height hh and radius rr is inscribed, as shown, inside a sphere of radius 66 cm.
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The base of the cone is ss cm below the xx-axis.

Find the value of ss which maximises the volume of the cone.
*You must use calculus and show any derivatives that you need to find when solving this problem.*

*You do not need to prove that the volume you have found is a maximum.*
Achievement
Differentiate f(x)=3x+24f(x)=\sqrt[4]{3x+2}.
Achievement
Find the xx-value at which a tangent to the curve y=6xe3xy = 6x - e^{3x} is parallel to the xx-axis.

*You must use calculus and show any derivatives that you need to find when solving this
problem.*