• TOC
  • Courses
  • Blog
  • Twitch
  • Shop
  • Search
    • Courses
    • Blog
    • Subreddit
    • Discord
    • Log in
    • Sign up
    • ▾Calculus 1
      • ▸Limits and continuity
        • •Intro to calc 1
        • •Estimating limits from graphs
        • •Estimating limits from tables
        • •Intro to continuity
        • •Finding and classifying discontinuities
        • •Finding the value that makes the function continuous
      • ▸Derivatives: definition and basic derivative rules
        • •Proving differentiable implies continuous
        • •Derivative of a function from first principles
        • •Finding the tangent or normal line through the given point
        • •Constant rule
        • •Constant multiple rule for derivatives
        • •Sum, difference, and power rules for derivatives
        • •Product rule
        • •Proving the product rule
        • •Quotient rule
        • •Derivatives of trig functions
        • •Proving properties of even and odd functions (calculus 1)
        • •Leibniz's derivative notation
        • •Logarithmic functions
      • ▾Derivatives: composite, implicit, and inverse functions
        • •Derivative at a point from first principles
        • •Derivatives of exponential functions
        • •Derivatives of logarithmic functions
        • ▸Derivatives of hyperbolic and inverse hyperbolic functions
          • •Using the derivatives of the hyperbolic functions
          • •Proving the derivatives of the hyperbolic functions
          • •Proving the derivatives of the inverse hyperbolic functions
        • •Derivatives of inverse trig functions
        • •Derivatives of transcendental functions
        • •Derivatives of trigonometric functions under transformations
        • •Derivative using u-substitution
        • •Determining derivatives from graphs
        • •Higher order derivatives
        • •Chain rule
        • •Derivatives of inverse functions
        • •Choosing the derivative rules to use
      • ▸Applying derivatives to analyze functions
        • •Applications of trigonometric derivatives
        • •Extreme value theorem
        • •First derivative test
        • •Mean value theorem
        • ▸Monotonic intervals and functions
          • •Intro
          • •Proofs
        • •Related rates
        • •Second derivative test
        • •Concavity
        • •Factoring a cubic polynomial with a double root
        • •Graphing using derivatives
        • ▸Special points
          • ▸Finding critical values from graphs
            • •Lesson
            • •Practice
          • •Finding critical values using derivatives
          • ▸Inflection points
            • •Graphically finding points of inflection
            • •Using the second derivative to find points of inflection
          • •Classifying stationary points
          • •Sketching polynomials using stationary points
        • •Bisection method
        • •Newton's method
        • •False position method
        • •L'Hopital's rule
      • ▸Integrals
        • •Basic integration problems
        • ▸Integration by u-substitution
          • ▸Integration by u-substitution (less difficult)
            • •Lesson
            • •Practice
          • •Integration by u-substitution (more difficult)
          • •Integrating exponential functions by u-substitution
        • •Visually determining antiderivative
      • ▸Applications of integrals
        • •Proving the formula for the area of a circle
        • •Area between two curves
        • ▸Solids of revolution
          • •Disc and washer methods (circular cross sections)
          • •Volumes of solids with known cross sections
          • •Shell method
          • •Volume of a sphere (calculus \(2\))
          • •Volume of a cone (calculus 2)
     › Calculus 1 › Derivatives: composite, implicit, and inverse functions

    Derivatives of trigonometric functions under transformations

    Conclude by giving your students these challenges:

    • Square inside a Semi-Circle by Hieu Huy Nguyen
    • Secret Transmissions by NRICH
    • Changing Places by NRICH
    • Skipped Counts

    Find the area of the green rectangle:

    Solution: Here's the solution. My method differs, and is preferable. It deviates immediately after finding the equations

    $$\begin{align} & ab = 12 \\ & 9b - a = 23 \end{align}$$

    Here's what I did to avoid guess-and-check: First, I find \(w\) in terms of \(h.\)

    $$\begin{align} & ab = 12 \\[0.5em] & a = \dfrac{12}{b} \\[0.5em] \end{align}$$

    Then I plug this into the second equation, and do some algebra:

    $$\begin{align} & 9b - \dfrac{12}{b} = 23 \\[0.5em] & 9b^2 - 12 = 23b \\ & 9b^2 - 23b - 12 = 0 \\ & (9b + 4)(b - 3) = 0 \end{align}$$

    This gives the solutions \(h = -4/9, 3.\) But \(b\) is a length, and thus can't be negative. So \(b = 3.\) From this, it's easy to see the area of the green rectangle is \(24.\)

    YouTube videos

    • 1213Differentiating Trigonometric Functions (1 of 2: Key results & chain rule)
      Eddie Woo
    • 1214Differentiating Trigonometric Functions (2 of 2: Example using quotient rule)
      Eddie Woo
    • 1215Calculus of Trigonometric Functions (1 of 3: Using visual intuition)
      Eddie Woo
    • 1216Calculus of Trigonometric Functions (2 of 3: An alternative version of first principles)
      Eddie Woo
    • 1217Calculus of Trigonometric Functions (3 of 3: Proving the basic derivative)
      Eddie Woo
    • 23031Learn to find the derivative of sine minus theta
      Brian McLogan
      Find the derivative:
      \(f(x) = 4\sin x - x\)
    • 17731How to find the derivative of a function with sine
      Brian McLogan
      Find the derivative:
      \(f(x) = 2\sin x\)
    • 14479Learn to find the derivative of a function with cosine
      Brian McLogan
      Find the derivative:
      \(f(x) = \dfrac{\cos x}{2}\)