CODEWITHSUNDEEP
pythontrigonometry
crazicrafter1
crazicrafter1

Reputation: 323

Python degrees defaulting to radians

I'm trying to print out the x,y value for a line with a certain degree which intersects a circle with a specified radius.

Lets say for example that the line is pointing straight up at 90 degrees.

import math

degree = 90
radius = 10
x = radius * math.cos(degree)
y = radius * math.sin(degree)

print(x,y)

This prints out -4.480736161291701 8.939966636005579 but according to my calculator is supposed to print 0 10 on deg.

I have already tried adding math.radians and math.degrees before the degree var in the x = and y =, but it doesn't come out correctly any time I've tried. The link I found to the point where a line with degree intersects a circle is here, the sin/cos values are flipped 'tho for the x and y value in the solution.

Simply said, how would I make the 90 be in degrees instead of radians to get the correct x,y?

EDIT:

by adding math.radians:

x = radius * math.cos(math.radians(degree))
y = radius * math.sin(math.radians(degree))

it returned 6.123233995736766e-16 10.0

~~~

by adding math.degrees:

x = radius * math.cos(math.degrees(degree))
y = radius * math.sin(math.degrees(degree))

it returned -2.995153947555356 -9.540914674728182

Upvotes: 2

Views: 7902

Answers (4)

Bumy Goldson
Bumy Goldson

Reputation: 1

If you're writing a somewhat longer code, you can make your code work in degrees by putting in the following lines in the beginning:

from math import sin, cos, tan, asin, acos, atan
from math import radians as rad, degrees as deg

def s(x):
    return sin(rad(x))

def c(x):
    return cos(rad(x))

def t(x):
    return tan(rad(x))

def sa(x):
    return deg(asin(x))

def ca(x):
    return deg(acos(x))

def ta(x):
    return deg(atan(x))

Then, throughout your code, instead of typing sin(90) you would type s(90), or for arcsin(90) you would type sa(90). (I couldn't make the code word as for arcsine, since as is already a Python word)

Now, you would just type up your code as though it were in degrees and everything should work out fine.

Upvotes: 0

user1767754
user1767754

Reputation: 25134

All angles in most of the math libraries are in radians. The input to math.cos should be radians but you are passing in degrees. 

import math

degree = 90
radius = 10
x = radius * math.cos(math.radians(degree))
y = radius * math.sin(math.radians(degree))
print x,y
>0, 10

math.radians is nothing more than doing (pi * degree / 180 )

Upvotes: 1

Olivier Melançon
Olivier Melançon

Reputation: 22324

In Python, you can use math.radians to convert from degrees to radians. Note that it is not just Python that defaults to radians, it is usually the standard in mathematics to talk about angles in radians.

Although, in general, you can always use the conversion formula

radians = pi * degrees / 180

Upvotes: 1

njwfish
njwfish

Reputation: 108

You can use math.radians(degree) to convert to radians. All python's default trig functions work in radians. So your code becomes:

import math

degree = 90
radius = 10
x = radius * math.cos(math.radians(degree))
y = radius * math.sin(math.radians(degree))

print(x,y)

And this produces the correct result: 6.123233995736766e-16 10.0, with some odd floating point behavior you can fix with appropriate rounding.

Upvotes: 0

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