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© 1999 T
EXAS
I
NSTRUMENTS
I
NCORPORATED
TI
-
34
Û
: A Guide for Teachers
10
Trig Functions
Overview
Students practice solving sine, cosine, and tangent
ratios, and solve problems involving trigonometric
ratios.
Math Concepts
• multiplication
• division
• trigonometric
ratios
Materials
• TI
-
34
Û
• pencil
• student activity
(page 12)
Introduction
Introduce the trigonometric ratios to students.
sin = opposite leg
¾
hypotenuse
cos = adjacent leg
¾
hypotenuse
tan = opposite leg
¾
adjacent leg
1.
Have students find the trigonometric ratios for
the triangle using the above definitions. Round to
the nearest hundredth if necessary. (Use
%
‚
for rounding.)
a.
sin C
3
¾
5 = 0.6
b. cos
C
4
¾
5 = 0.8
c.
tan
C
3
¾
4 = 0.75
d. sin
A
4
¾
5 = 0.8
e.
cos
A
3
¾
5 = 0.6
f.
tan
A
4
¾
3 = 1.33
2.
Have students find the value of each ratio using
the TI
-
34
Ö
. Round to the nearest 10 thousandth.
a.
sin 71°
0.9455
b. tan 31°
0.6009
c.
cos 25°
0.9063
3.
Have students find the measure of each angle
using the TI
-
34
Ö
. Round to the nearest degree.
a.
sin
B
= 0.4567
27 degrees
b. cos
A
= 0.6758
47 degrees
c.
tan
C
= 5.83
80 degrees
³
To set 2 decimal places:
1. Press
%
‚
.
F0123456789
2. Press 2 to select 2
decimal places and press
<
.
³
To find sin 65°,
1. Press
%
‚
4
.
2. Press
%
B
<
.
sin(
3. Enter 65, and press
E
<
.
sin(65)
0.9063
³
To find
A when sin A= 0.2756:
1. Press
%
‚
0.
2. Press
%
B
"
<
.
sin
-1
(
3. Enter 0.2756, and press
E
<
.
sin
-1
(0.2756
¹
¹
16
5
4
3
B
C
A