Sharp EL-9900 - Manual (Page 119)

4
Advanced Keyboard/TRIGONOMETRY USING THE SHARP EL-9900
Copyright © 2002, Sharp Electronics Corporation. Permission is granted to photocopy for educational use only.
1. Verify the double angle formula sin 2
θ = 2 sin θ cos θ, by graphing Y1 = sin
(2x) and Y2 = 2 sin x cos x and show that they are in fact the same graph.
2. Turn the calculator on and press Y= . Press CL to clear Y1 of an old
expression. Press
▼ CL to clear additional expressions.
3. Make sure the calculator is in radian mode by pressing 2ndF SET UP ,
B (DRG) and 2 (Rad). Press 2ndF QUIT to exit the menu.
4. Now enter sin (2x) for Y1 by pressing sin ( 2 X/
θ/T/n ) ENTER
and the 2 sin x cos x for Y2 by pressing 2 sin X/
θ/T/n cos X/θ/T/n
ENTER .
5. Set your viewing window by pressing ZOOM E (TRIG) 1 (sin x).
6. They appear as one graph. An invalid formula or identity would result in
two graphs.
GRAPHICAL VERIFICATION OF FORMULAS
AND IDENTITIES