Wednesday, November 2, 2011

4.5 Graphs of Sine and Cosine Functions


or




The constant factor of a in y=asinx acts as a scaling factor- a vertical stretch or vertical shrink of the basic sine curve. If , the basic sine curve is stretched, and if , the basic sine curve is shrunk. The result is that the graph of y=asinx ranges between -a and a instead of -1 and 1.


The amplitude of and represents half the distance between the maximum and minimum values of the function and is given by:


Let b be a positive real number. The period of and is given by:



Note that if , the period of is greater than and represents a horizontal stretching of the graph of . Similarly, if , the period of is less than and represents a horizontal shrinking of the graph of .


The constant c creates horizontal translations (shifts) of the basic sine and cosine curves.


The graph of is shifted by an amount of . The number is the phase shift.


The left and right endpoints of a one-cycle interval can be determined by solving the equations and .

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