Trigonometric Functions and Graphs

Graph and transform sin, cos, and tan functions for IB Maths. Find amplitude, period, and phase shift.

Trig function graphs are central to IB Maths. You need to identify transformations and solve equations graphically.

General Form

y=asin(b(xc))+dy = a\sin(b(x - c)) + d

  • a|a| = amplitude.
  • Period = 2πb\frac{2\pi}{|b|} (or 360°b\frac{360°}{|b|}).
  • cc = phase shift (horizontal).
  • dd = vertical shift.

Key Graphs

  • sinx\sin x: starts at 0, period 2π2\pi, range [1,1][-1, 1].
  • cosx\cos x: starts at 1, period 2π2\pi, range [1,1][-1, 1].
  • tanx\tan x: period π\pi, asymptotes at x=π2+nπx = \frac{\pi}{2} + n\pi.

Worked Example

y=3sin(2xπ3)+1y = 3\sin(2x - \frac{\pi}{3}) + 1.

Amplitude: 3. Period: π\pi. Phase shift: π6\frac{\pi}{6} right. Vertical shift: 1 up. Range: [2,4][-2, 4].

Solving Trig Equations

Find all solutions in [0,2π][0, 2\pi]: sinx=12\sin x = \frac{1}{2}x=π6,5π6x = \frac{\pi}{6}, \frac{5\pi}{6}.

Practice Problems

    1. State amplitude, period, and range of y=2cos(3x)1y = 2\cos(3x) - 1.
    1. Solve 2sinx1=02\sin x - 1 = 0 for 0x2π0 \leq x \leq 2\pi.

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Key Takeaways

  • Amplitude = a|a|. Period = 2πb\frac{2\pi}{|b|}.

  • Phase shift = cc (right). Vertical shift = dd.

  • Use GDC to verify graphs.

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