The equation of a curve is y=3−4sin⁡2xy = 3 - 4\sin 2x.

  1. (i)

    State the minimum and maximum value of yy.

  2. (ii)

    Sketch the curve y=3−4sin⁡2xy = 3 - 4\sin 2x for 0≤x≤2π0 \le x \le 2\pi

Work through it with AI →

It won't just hand you the answer — it asks where you're stuck.How the checker works

Worked solution

6(i)

1. Identify the range of the sine function

We know that −1≤sin⁡2x≤1-1 \le \sin 2x \le 1.

2. Calculate the minimum and maximum values of y

Maximum value of yy occurs when sin⁡2x=−1\sin 2x = -1:
ymax⁡=3−4(−1)=7y_{\max} = 3 - 4(-1) = 7

Minimum value of yy occurs when sin⁡2x=1\sin 2x = 1:
ymin⁡=3−4(1)=−1y_{\min} = 3 - 4(1) = -1

Answer

Minimum value = −1-1, Maximum value = 77

6(ii)

1. Determine the amplitude, period, and principal axis of the function

For y=3−4sin⁡2xy = 3 - 4\sin 2x:

  • Principal axis: y=3y = 3
  • Amplitude: 44
  • Period: 2π2=π\frac{2\pi}{2} = \pi

2. Identify the key coordinates for the first period ($0 \le x \le \pi$)

The curve is an inverted sine wave (due to the negative sign) shifted up by 3.
Key points for the first period:

  • Start: (0,3)(0, 3)
  • Minimum: (π4,3−4)=(π4,−1)(\frac{\pi}{4}, 3 - 4) = (\frac{\pi}{4}, -1)
  • Midpoint: (π2,3)(\frac{\pi}{2}, 3)
  • Maximum: (3π4,3+4)=(3π4,7)(\frac{3\pi}{4}, 3 + 4) = (\frac{3\pi}{4}, 7)
  • End of first period: (π,3)(\pi, 3)

3. Identify the key coordinates for the second period and sketch the full graph

The pattern repeats for π≤x≤2π\pi \le x \le 2\pi:

  • Minimum: (5π4,−1)(\frac{5\pi}{4}, -1)
  • Midpoint: (3π2,3)(\frac{3\pi}{2}, 3)
  • Maximum: (7π4,7)(\frac{7\pi}{4}, 7)
  • End: (2π,3)(2\pi, 3)
    Draw a smooth curve through all these points.
Answer

A smooth sine curve starting at (0,3)(0, 3), going down to a minimum at (π4,−1)(\frac{\pi}{4}, -1), crossing the principal axis at (π2,3)(\frac{\pi}{2}, 3), reaching a maximum at (3π4,7)(\frac{3\pi}{4}, 7), and returning to (π,3)(\pi, 3). This pattern repeats exactly once more, ending at (2π,3)(2\pi, 3).

AI analysis — may contain mistakes.

Worked this one out on paper? Snap your steps and Gigle's AI math checker will circle the step where it went wrong.

More questions on this topic

  1. 1函数f(x)=sin⁡x−cos⁡xf(x)=\sin x-\cos x,则函数f(x)f(x)的最大值为()(\quad) A. 22 B. 2\sqrt{{2}} C. 00 D. −2-2
  2. 2Using Rcos⁡(θ−α)R \cos(\theta - \alpha), where R>0R > 0 and 0∘≤α≤90∘0^\circ \le \alpha \le 90^\circ, solve the equation 5cos⁡θ+8sin⁡θ=65 \cos \theta + 8 \sin \theta = 6…
  3. 3State the range of principal values of tan⁡−1x\tan^{-1} x. The curve y=a+bcos⁡cxy = a + b \cos c x is shown below for 0≤x≤3π20 \le x \le \tfrac{3\pi}{2}…
  4. 4The diagram below shows a portion a plastic fibre cable, which allows light waves to pass through. The path of the light…
  5. 5The diagram shows a wind turbine with blade 25 m25\text{ m} in length. The centre of the wind turbine is 35 m35\text{ m} fro…