Casio fx-350MS Booklet page 23

CHAPTER 7
ABC is a triangle in which AB = 4cm, AC = 5.4cm and BC = 8cm. Find
Example 3
∠
ACB
OPERATION
1 . Use the formula
cos
calculator is in COMP/Deg mode.
5 • 4
2
– 4 x
( 2
¡
=
X 8
∠
cos ACB = 0.893055555.
2 . To determine ∠
ACB
-1
cos
SHIFT
cos
∠
Hence, ACB is approximately 26.74°.
Answers to Quick Check 1
1 (a) -381.078125 (b) 5/42
3 (a) 7,079.457844 (b) 2.724069927
7 (a) 1.966637001 (b) 4.289146637
° 1
(c) -166°9'27.94''
9 cos . 0
Answers to Quick Check 2
1 (a) 43,758 (b) 55,440
3 (a) 1,951 (b) 65.03333333
7 (a) 35.73496445° (b) 0.9125573
Solutions of Triangles
.
B
2 + 2
AC BC
∠ =
ACB
× ×
2 AC
2
x + 8
=
X 5 •
, press
=
(c) 210,034.1658
(c) 21.10019602,@
0.368267893
(c) 11.35402128
10 5.595526906
(c) 362,880 2 5, 10, 13
(c) 19.78633086 4 0.201653658
A
5.4cm
4cm
8cm C
− 2
AB
to determine cos
BC
2
x
5.4
4
Ans¡(2 X5.4 X8
cos
2 (a) 0.034899496 (b) 1
4 755.0922277 5 1,096.633158
8 (a) 178°11'23.5'' (b) 133°41'24.5''
5 95,040
∠
ACB . Ensure
2 2 2
+8 -4
77.16
0.893055555
-1
Ans
26.74024593
(c) 2
6 -12.05796327
6 11,400
20