问题
My python interpreter is acting funky when I use the math.cos() and math.sin() function. For example, if I do this on my calculator:
cos(35)*15+9 = 21.28728066
sin(35)*15+9 = 17.60364655
But when I do this on python (both 3.2 and 2.7)
>>> import math
>>> math.cos(35)*15+9
-4.5553830763726015
>>> import math
>>> math.sin(35)*15+9
2.577259957557734
Why does this happen?
EDIT: How do you change the Radian in Python to degrees, just in case?
回答1:
This is being caused by the fact that you are using degrees
and the trigonometric functions expect radians as input:sin(radians)
The description for sin is:
sin(x)
Return the sine of x (measured in radians).
In Python, you can convert degrees to radians with the math.radians function.
So if you do this with your input:
>>> math.sin(math.radians(35)) * 15 + 9
17.60364654526569
it gives the same result as your calculator.
回答2:
The following Python methods can be used to convert radians to degrees or vice versa:
math.degrees
math.radians
Using your example:
>>> from math import cos, sin, radians
>>> sin(radians(35)) * 15 + 9
17.60364654526569
>>> cos(radians(35)) * 15 + 9
21.28728066433488
Weird calculator... takes degrees but returns radians.
回答3:
cos(35)[degree] = 0.819 * 15 + 9 = 21.285 <-- Your calculator
sin(35)[radian] = -0.428 * 15 + 9 = 2.577 <-- Python
来源：https://stackoverflow.com/questions/8691800/unusual-math-with-incorrect-results