Chapter 3 CNC Math 65
The six trigonometric functions are defined relative to the relationships
between two sides of the right triangle, Figure 3-21. These relationships are:
• Sine (sin). The ratio of the opposite side to the hypotenuse.
Sine a =
Opposite side
=
A
Hypotenuse C
• Cosine (Cos). The ratio of the adjacent side to the hypotenuse.
Cosine a =
Adjacent side
=
B
Hypotenuse C
• Tangent (Tan). The ratio of the opposite side to the adjacent side.
Tangent a =
Opposite side
=
A
Adjacent side B
• Cotangent (Cot). The ratio of the adjacent side to the opposite side. It
is the reciprocal of the tangent function.
Cotangent a =
Adjacent side
=
B
Opposite side A
• Secant (Sec). The ratio of the hypotenuse to the adjacent side. It is the
reciprocal of the cosine function.
Secant a =
Hypotenuse
=
C
Adjacent side B
• Cosecant (Csc). The ratio of the hypotenuse to the opposite side. It is
the reciprocal of the sine function.
Cosecant a =
Hypotenuse
=
C
Opposite side A
C (hypotenuse)
B
A
c
b
a
Figure 3-21. The hypotenuse is always the
longest side (leg) of a right triangle.