Digital Signal Processing Reference
In-Depth Information
q
2
c
b
q
1
a
Figure 4.1: A right triangle.
The sine function gives us the ratio of the length of the opposite side (b) to the
length of the hypotenuse (c). In other words,
sin(
1
) =
b
c
:
1
functions (also called arccos and arcsin) give us the angle
1
from the ratio of the sides.
1
The cos
and sin
4.2
The Number
It is impossible to talk about sine and cosine functions without talking about the
constant , the ratio of a circle's diameter to its circumference (see Figure 4.2). You
probably remember the equation:
circumference = 2r, where r is the circle's radius.
Length
around is
2 r
p
−r
+r
Figure 4.2: An example circle.
