12
—
S
HEET
M
ETAL
/HVAC
P
RO
C
ALC
LAW OF COSINES / NON-90 DEGREE TRIANGLE KEYS
Ç 9
Law of Cosines
— These keys are used for non-90
degree triangle mathematics and are incorporated
with Right Triangle mathematics (using “Measured”
non-90 degree and “Calculated” Right Triangles),
particularly, for finding the dimensional relationship
of distance and alignment between two or more
objects. The overall purpose of these calculations is
to develop the duct and/or fittings required to fill a
space.
These keys calculate the opposite angles A, B, and
C given entry of Side a, b, and c using the Law of
Cosines (see Storage Registers a, b, and c below)
and triangle area using Heron’s Theorem. They also
enable the computation of Right Triangle lengths “
x
,”
“
y
,” “
r
” and Theta, for determining Offset, Length,
and Angle.
Press
Result
1
Angle A
2
Angle B
3
Angle C
4
Area (using formula for Heron’s Theorem)
5
Redisplays entered Side a
6
Redisplays entered Side b
7
Redisplays entered Side c
Ç 4
Storage Register “a”
— Enters Side “a” of a
Measured Triangle (e.g., if Side “a” is five feet, enter
5 f Ç 4
).
Ç 5
Storage Register “b”
— Enters Side “b” of a
Measured Triangle.
Ç 6
Storage Register “c”
— Enters Side “c” of a
Measured Triangle.
