TI-58/TI-59 Week: Law of Cosines
Introduction
[ A ]: stores either the angle θ or a
[ B ]: stores the length of side b
[ C ]: stores the length of side c
[ D ]: calculates the length of side a:
a^2 = b^2 + c^2 - 2 * b * c * cos θ
[ E ]: calculates the angle θ
cos θ = (b^2 + c^2 - a^2) / (2 * b * c)
The angle θ is opposite slot of side a.
Program Listing
000 76 LBL
001 11 A
002 42 STO
003 01 01
004 92 INV SBR (RTN)
005 76 LBL
006 12 B
007 42 STO
008 02 02
009 92 INV SBR
010 76 LBL
011 13 C
012 42 STO
013 03 03
014 92 INV SBR
015 76 LBL
016 14 D
017 43 RCL
018 02 02
019 33 x^2
020 85 +
021 43 RCL
022 03 03
023 33 x^2
024 75 -
025 02 2
026 65 ×
027 43 RCL
028 02 02
029 65 ×
030 43 RCL
031 03 03
032 65 ×
033 43 RCL
034 01 01
035 39 cos
036 95 =
037 34 √
038 42 STO
039 04 04
040 INV SBR
041 76 LBL
042 15 E
043 53 (
044 43 RCL
045 02 02
046 33 x^2
047 85 +
048 43 RCL
049 03 03
050 33 x^2
051 75 -
052 43 RCL
053 01 01
054 33 x^2
055 54 )
056 55 ÷
057 53 (
058 02 2
059 65 ×
060 43 RCL
061 02 02
062 65 ×
063 43 RCL
064 03 03
065 54 )
066 95 =
067 02 INV
068 39 cos (arccos)
069 42 STO
070 04 04
071 92 INV SBR
Examples
Calculating a:
Set the TI-58/TI-59 to Degrees mode:
Input:
50° [ A ]
45 [ B ] (b)
35 [ C ] (c)
[ D ] returns a: 35.00312885
85° [ A ]
100 [ B ] (b)
70 [ C ] (c)
[ D ] returns a: 116.9607609
Calculating θ:
52 [ A ] (a)
38 [ B ] (b)
49 [ C ] (c)
[ E ] returns θ: 72.15813198
80 [ A ] (a)
60 [ B ] (b)
65 [ C ] (c)
[ E ] returns θ: 79.47338145
Note: The next post will be on July 23, 2022.
Eddie
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