Biomedical Engineering Reference
In-Depth Information
Fig. A.4
A right triangle
A
c
b
= 90
C
B
opposite
a
Table A.1
Trigonometric
functions of some angles
Angle (deg)
Angle (rad)
sine
cosine
tangent
0
0
0
1.000
0
30
(1/6)
π
0.500
0.866
0.577
45
(1/4)
π
0.707
0.707
1.000
60
(1/3)
π
0.866
0.500
1.732
90
(1/2)
π
1.000
0
1
180
π
0
1.000
0
270
(3/2)
π
1.000
0
1
360
2
π
0
1.000
0
In a right triangle (Fig.
A.4
), the Pythagorean theorem can be expressed as in
Pythagorean equation:
c
2
a
2
b
2
¼
þ
:
In any triangle ABC, shown in Fig.
A.3
, the following relations are defined:
sin
a
¼
sin
b
¼
sin
γ
,
c
c
2
a
2
b
2
¼
þ
2
ab
cos
γ
:
is equal to 90
, which corresponds to the case of a right triangle, the above
equation degenerates into the Pythagorean formula, as cos 90
¼
If
γ
0. The values of
sine, cosine, and tangent of some angles are given in Table
A.1
.
Linear Equation
A linear equation has the general form
y
¼
a
þ
bx
,
where
a
and
b
are constants. This equation is referred to as being linear because the
graph of
y
vs.
x
is a straight line as shown in Fig.
A.5
. The constant
a
, called the
