OARLY

Applications of Derivatives [Video Tutorial]

This tutorial covers material encountered in chapter 10 of the VCE Mathematical Methods Textbook, namely:

  • Tangents and normals
  • Finding and classifying stationary points
  • Maximum and minimum values of a function
  • Motion in 1-dimension

Q1 – Find the Tangent Equation at the Given Point

https://youtu.be/AqPNNzjvdaw

Q2 – Find the Tangent Equation at the Given Point and More

https://youtu.be/0ueyG0rh_5I

Q3 – Rate of Change of the Area of a Circle

https://youtu.be/O1t04oovuGE

Q4 – Stationary Points of Functions

https://youtu.be/wmo95NV15nQ

Q5 – Minimum Value of a Function

https://youtu.be/FxIoilSF5Ew

Q6 – Motion in 1-Dimension – Velocity and Acceleration

https://youtu.be/84OchBDcyNc

Q7 – Rate of Increase

https://youtu.be/Law_DYfth1w

Worksheet

Q1. Find the equation of the tangent to the following functions at the given points

(a) \(f(x)=x^3-7x^2+5x \), at \( x=2 \)

(b) \(f(x)=x^3-7x^2+14x-3\), at [/latex]x=1[/latex]

(c) \(g(x)=\ln(x+1)\), at \(x=e-1\)

(d) \(g(x)=3\sin(\frac{x}{2})\), at \(x=\frac{\pi}{2}\)

(e) \(h(x)=2\cos(x)\), at \(x=\frac{3\pi}{2}\)

(f) \(h(x)=\ln(x^2)\), at \(x=-\sqrt{e}\)

Q2. (a) Find the equation of the tangent to the function \( f(x)=x^3-8x^2+15x \) at the point with coordinates \((4,-4)\).

(b) Find the coordinates of the point where the tangent meets \(f\) again.

Q3. Use the formula for the area of a circle \((A=\pi r^2)\) to find:

(a) The average rate of change of the area of a circle as the radius of the circle increases from \(r=3\) to \(r=4\)

(b) The instantaneous rate of change of the area with respect to the radius when \(r=4\)

Q4. Find the stationary points of the following functions and classify their nature:

(a) \(f(x)=2x^3-3x^4\)

(b) \(g(x)=x^3-4x+2\)

(c) \(h(x)=x^3-6x^2+3\)

Q5. Find the absolute minimum and its value of \(f(x)=e^{2x}+e^{-2x}\) for \(x\in[-3,3]\)

Q6. A car is travelling in a straight line away from a point \(P\). Its distance from \(P\) after \(t\) seconds is \(\frac{1}{4}e^t\) metres. Find the velocity and acceleration of the vehicle at \(t=0, 1, 2, 4\)

Q7. The diameter (\(D\) cm) of a read oak tree (not to be confused with red oak), \(t\) years after March 21, 2000 is given by \(D=40e^{kt},\,k\in\R\)

(a) Show that \(\dfrac{dD}{dt}=cD\) for some constant \(c\)

(b) If \(k=0.3\) find the rate of increase of \(D\) when \(D=120\)

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