Introducing the Topic
In this chapter, you and your students will learn how to verify trigonometric
formulas and identities graphically. The left and right sides of an equality can be
graphed by the calculator as Y1 and Y2. Verification is made by viewing Y1 and
Y2 as the same graph, hence equivalent expressions.
Calculator Operations
To verify the double angle formula sin 2
θ
= 2 sin
θ
cos
θ
, you will graph the "sin
2
θ
" as Y1 = sin (2
x
) and the "2 sin
θ
cos
θ
" as Y2 = 2 sin
x
cos
x
and show that
they are in fact the same graph. To do this you will turn the calculator on and
press Y= . Press CL to clear Y1 of an old expression. Press
▼
CL to clear
additional expressions. Make sure the calculator is in radian mode by pressing
2ndF SET UP , touch
B DRG
, and double touch
2 Rad
. Press 2ndF QUIT
to exit the menu.
Now enter sin (2
x
) 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 . Set your viewing window by pressing WINDOW EZ , touch
5
, touch
on the screen, touch
6
–
2
π
<X,<2
π
, touch on the screen, and touch
5
–
5<Y<5
.
10
Graphical Verification of Formulas and Identities/TRIGONOMETRY USING THE SHARP EL-9600
GRAPHICAL VERIFICATION OF
FORMULAS AND IDENTITIES
Chapter three
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