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4.5 Sinusoidal Graphs. Sketching and Writing Equations. Graphs of sine and cosine functions. Sinusoidal Graphs. Periodic Function. Functions whose graphs have a repeating pattern. Sinusoidal Graphs. Period. The horizontal length of each cycle in a periodic graph. Midline.
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4.5Sinusoidal Graphs Sketching and Writing Equations
Graphs of sine and cosine functions. Sinusoidal Graphs Periodic Function Functions whose graphs have a repeating pattern. Sinusoidal Graphs Period The horizontal length of each cycle in a periodic graph. Midline The horizontal line halfway between a sinusoid’s max/min values.
Characteristics of the Sine Function • The domain is the set of all real numbers. • The range consists of all real numbers from -1 to 1, inclusive. • The sine function is an odd function (symmetric with respect to the origin). • The sine function has a period of 2π • Midline is the x-axis
3 2 1 -1 -2 -3 Period y = sinx pattern starts pattern starts pattern starts 1 period 1 period Period= 2
Characteristics of the Cosine Function • The domain is the set of all real numbers. • The range consists of all real numbers from -1 to 1, inclusive. • The cosine function is an even function (symmetric with respect to the y-axis). • The cosine function has a period of 2π • Midline is the x-axis
Period y = cosx 3 2 1 -1 -2 -3 pattern starts pattern starts pattern starts 1 period 1 period Period = 2
Period 3 2 1 -1 -2 -3 pattern starts pattern starts 1 period Period=
3 2 Period 3 2 1 -1 -2 -3 pattern starts pattern starts 1 period Period =
Amplitude Amplitude Half the distance between the maximum and minimum of a sinusoidal graph.
Amplitude 3 2 1 -1 -2 -3 max. Amplitude min. Amplitude = 1
Amplitude max. 3 2 1 -1 -2 -3 Amplitude Amplitude = 2 min.
Amplitude max. 3 2 1 -1 -2 -3 Amplitude min. Amplitude = 1
Amplitude Amplitude = 2 3 2 1 -1 -2 -3 max. 3 Amplitude min.
Amplitude = Period = Sinusoidal Graphs General Form of Equations
Sinusoidal Graphs y = -4cos5x y = 3sin4x Amplitude = Amplitude = Period = Period =
Writing Equations Answer these questions first: • Is it a “sin” or “cos” graph? • What is the amplitude? • What is the period? • Is the graph reflected? • Is it shifted up/down? • Is it shifted left/right?
Writing Equations b = a = 4 Write an equation: cosine graph amplitude = 4 Period = b = = 2
Writing Equations b = a = 3 Write an equation: sine graph amplitude = 3 Period = 4 b =
Writing Equations b = Write an equation: sine graph amplitude = 2 Period = 3 Reflected over x-axis a = ±2 b =
Write an equation: cosine graph amplitude = ½ Period = Reflected over x-axis Writing Equations b = Invert and multiply! a = b =
Writing Equations Write an Equation Sine graph Amplitude = 5 Period = Shifted up 2 a = b = Changing the midline causes vertical shifts
Sinusoidal Graphs “sin” a =1 b = Period = 3 2 1 -1 -2 -3 Amplitude = 1 y = sin2x
Sinusoidal Graphs “sin” 2 Period = a =3 b = Amplitude = 3 3 2 1 -1 -2 -3 y = 3sinx
Sinusoidal Graphs “cos” a =1 Period = b = 1 3 2 1 -1 -2 -3 Amplitude =
Sinusoidal Graphs “cos” -2 a = b = Period = 3 3 2 1 -1 -2 -3 Amplitude = 2 Reflected over x-axis!
Sinusoidal Graphs “cos” b = Period = 6 a = -3 Amplitude = 3 3 2 1 -1 -2 -3 Reflected over x-axis!
Graphing Sinusoidal Functions 3 2 1 -1 -2 -3 y = 3sin4x
Graphing Sinusoidal Functions 3 2 1 -1 -2 -3 y = 2sinx
Graphing Sinusoidal Functions 3 2 1 -1 -2 -3 y = -3sin2x
Graphing Sinusoidal Functions 3 2 1 -1 -2 -3
Graphing Sinusoidal Functions 3 2 1 -1 -2 -3
Graphing Sinusoidal Functions 3 2 1 -1 -2 -3
Phase Shift • Horizontal translations of sine and cosine graphs. Right Left Phase Shift Phase Shift
right Phase Shift Amp = 3 T = P.S. =
left Phase Shift Amp = 2 T = P.S. =
Phase Shift “Cosine” Amplitude = 5 Period = Phase shift =
Phase Shift “sine” Amplitude = 3 Period = 4 Phase shift =