Texas Instruments TI-80 User Manual - Page 167

The Unit Circle and Trigonometric Curves You can use the parametric graphing feature of the TI.80 to show the relationship between the unit circle and any trigonometric curve. Problem Procedure Graph the unit circle and the sine curve to demonstrate graphically the relationship between them. Any function that can be plotted in function graphing can be plotted in parametric graphing by defining the X component as T and the Y component as F(T). Following this procedure to solve the problem. 1. Press 3 and select RADIAN, PARAM, and SIMUL. 2. Press ) and set the Window variables. TMIN = 0 TMAX = 2p TSTEP = .1 XMIN = .2 XMAX = 2p XSCL = pà2 YMIN = .3 YMAX = 3 YSCL = 1 3. Press ( and enter the expressions to define the unit circle centered at (L1,0). X1îT=COS Tì1 Y1î=SIN T Enter the expressions to define the sine curve. X2î=T Y2î=SIN T Turn off all other functions. 4. Press , to see the SIN function "unwrap" from the unit circle. Note: The "unwrapping" can be generalized. Replace SIN T in Y2î with any other trig function to "unwrap" that function. Applications 11-3