Sinusoidal Functions & Graphs (DP IB Applications & Interpretation (AI)): Revision Note

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Sinusoidal Functions & Graphs

What are the key features of sinusoidal graphs?

  • A sinusoidal graph is of the form

    • space y equals a sin left parenthesis b x right parenthesis plus d

    • space y equals a cos left parenthesis b x right parenthesis plus d

  • The y-intercept is at the point

    • (0, d) for space y equals a sin left parenthesis b x right parenthesis plus d

    • (0, a + d) for space y equals a cos left parenthesis b x right parenthesis plus d

  • The period of the graph is the length of the interval of a full cycle

    • This is fraction numerator 360 degree over denominator b end fraction

  • The maximum value is y = a + d

  • The minimum value is y = -a + d

  • The principal axis is the horizontal line halfway between the maximum and minimum values

    • This is y = d

  • The amplitude is the vertical distance from the principal axis to the maximum value

    • This is a

ib-ai-sl-2-2-3-sinusoidal-graphs

Examiner Tips and Tricks

  • Pay careful attention to the angles between which you are required to use or draw/sketch a sinusoidal graph

    • e.g.  0° ≤ x ≤ 360°

Worked Example

a) Sketch the graph space y equals 3 sin left parenthesis 2 x right parenthesis plus 1 for the values space 0 less or equal than x less or equal than 360.

2-2-3-ib-ai-sl-sinusoidal-graphs-a-we-solution

b) State the equation of the principal axis of the curve.

2-2-3-ib-ai-sl-sinusoidal-graphs-b-we-solution

c) State the period and amplitude.

2-2-3-ib-ai-sl-sinusoidal-graphs-c-we-solution

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Dan Finlay

Author: Dan Finlay

Expertise: Maths Subject Lead

Dan graduated from the University of Oxford with a First class degree in mathematics. As well as teaching maths for over 8 years, Dan has marked a range of exams for Edexcel, tutored students and taught A Level Accounting. Dan has a keen interest in statistics and probability and their real-life applications.