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# Python - math.cos() method example

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The `math.cos()` function returns the cosine of the specified angle in radians in the range `-1` to `+1`.

``````import math

print(math.cos( 0                  ) )  # 1   <-  0 degrees
print(math.cos( 1.5707963267948966 ) )  # ~0  <- ~90 degrees  ==  pi / 2
print(math.cos( 3.1415926535897932 ) )  # ~-1 <- ~180 degrees ==  pi
print(math.cos( 4.71238898038469   ) )  # ~0  <- ~270 degrees == -pi * (3 / 2)
print(math.cos( 6.2831853071795850 ) )  # ~1  <- ~360 degrees ==  pi * 2

print(math.cos( -1.5707963267948966) )  # ~0  <- ~-90 degrees == -pi / 2``````

Note: `6.123233995736766e-17`, `-1.8369701987210297e-16` and `6.123233995736766e-17` should be equal to `0` but they are not because of computation precision error.

## 1. Documentation

 Syntax ``math.cos(number)`` Parameters `number` - double value in radians. Result returns a numeric value between `-1` and `+1`, which represents the cosine of the angle. Description `cos` is a method that takes only one parameter and returns an approximation of `cos(x)` mathematical function result.

``````import math

x1 = 0.0
x2 = math.pi / 2

dx = math.pi / 9

Output:

``````cos( 0.0 rad) =  1.0

## 3. Working with degrees

``````import math

def calculate_cos(deg):
rad = (math.pi / 180) * deg

x1 = 0.0    # beginning of calculation in degrees
x2 = 90.0   # ending of calculation degrees

dx = 15.0   # calculation step in degrees

deg = x1

while deg <= x2:
y = calculate_cos(deg)
print("cos(", deg, " deg) = ", y)
deg += dx``````

Output:

``````cos( 0.0  deg) =  1.0
cos( 15.0  deg) =  0.9659258262890683
cos( 30.0  deg) =  0.8660254037844387
cos( 45.0  deg) =  0.7071067811865476
cos( 60.0  deg) =  0.5000000000000001
cos( 75.0  deg) =  0.25881904510252074
cos( 90.0  deg) =  6.123233995736766e-17``````

## 4. Reversed console plot example

``````import math

x1 = 0.0         # beginning of cosine chart
x2 = 3 * 3.14    # end of cosine chart

dx = 3.14 / 4.0  # x axis step
dy = 1.0 / 5.0   # y axis step

y1 = 0.0

string = ""

y = y1
while y < y2:
string += " "
y += dy

print(string, "+")

Output:

``````           +
+
+
+
+
+
+
+
+
+
+
+``````

## References

1. Cosine - Wikipedia