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Published byLorena Ellis Modified about 1 year ago

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Graphs of Sine and Cosine On to Section 4.4

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Graphical Analysis: graph the function in the given window by Domain:Range: Continuous Alternately increasing and decreasing in periodic waves Symmetry: Origin (odd function) BoundedAbsolute Max. of 1Absolute Min. of –1 No Horizontal AsymptotesNo Vertical Asymptotes End Behavior: anddo not exist

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The “Do Now” – first, graph the function in the given window by Other notes: This function is periodic, with period By definition, sin(t) is the y-coordinate of the point P on the unit circle to which the real number t gets wrapped So now let’s “explore” where this wavy graph comes from…

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Exploration – Graphing sin(t) as a Function of t Set your calculator to radian mode, parametric, and “simultaneous” graphing modes. Set Tmin = 0, Tmax = 6.3, Tstep = Set the (x, y) window to [–1.2, 6.3] by [–2.5, 2.5] Set X1T = cos(T) and Y1T = sin(T). This will graph the unit circle. Set X2T = T and Y2T = sin(T). This will graph sin(T) as a function of T.

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Exploration – Graphing sin(t) as a Function of t Now start the graph and watch the point go counterclockwise around the unit circle as t goes from 0 to in the positive direction. You will simultaneously see the y-coordinate of the point being graphed as a function of t along the horizontal t-axis. You can clear the drawing and watch the graph as many times as you need in order to answer the following questions. 1. Where is the point on the unit circle when the wave is at its highest? at the point (0,1) 2. Where is the point on the unit circle when the wave is at its lowest? at the point (0,–1) 3. Why do both graphs cross the x-axis at the same time? Both graphs cross the x-axis when the y-coordinate on the unit circle is zero.

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Exploration – Graphing sin(t) as a Function of t Now start the graph and watch the point go counterclockwise around the unit circle as t goes from 0 to in the positive direction. You will simultaneously see the y-coordinate of the point being graphed as a function of t along the horizontal t-axis. You can clear the drawing and watch the graph as many times as you need in order to answer the following questions. 4. Double the value of Tmax and change the window to [–2.4, 12.6] by [–5, 5]. Change the grapher “style” to show a moving cursor. Run the graph and watch how the sine curve tracks the y-coordinate of the point as it moves around the unit circle. 5. Explain from what you have seen why the period of the sine function is.

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Exploration – Graphing sin(t) as a Function of t Now start the graph and watch the point go counterclockwise around the unit circle as t goes from 0 to in the positive direction. You will simultaneously see the y-coordinate of the point being graphed as a function of t along the horizontal t-axis. You can clear the drawing and watch the graph as many times as you need in order to answer the following questions. 6. Challenge: Can you modify the calculator settings to show dynamically how the cosine function tracks the x-coordinate as the point moves around the unit circle? Leave all previous settings the same, except change Y2T to cos(T) check the graph!!!

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Now, a Complete Analysis of the Cosine Function by Domain:Range: Continuous Alternately increasing and decreasing in periodic waves Symmetry: y-axis (even function) BoundedAbsolute Max. of 1Absolute Min. of –1 No Horizontal AsymptotesNo Vertical Asymptotes End Behavior: anddo not exist

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Now, a Complete Analysis of the Cosine Function by Other notes: This function is periodic, with period By definition, cos(t) is the x-coordinate of the point P on the unit circle to which the real number t gets wrapped Using our transformational knowledge, how does the graph of cos(t) relate to that of sin(t)??? It is a horizontal shift by of the graph of sin(t)

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