Why getting ValueError : Math domain error in trig. function, math.asin() ?

[jahuja73]

Unable to see why error in output.
Tried on repl.it, as well as ideone.com; and get the same error.

#your code goes here
import math
 
# number
a = 2
print("asin(",a,") is = ", math.asin(a))

Output:

Traceback (most recent call last):
File "./prog.py", line 6, in <module>
ValueError: math domain error

[Serafim]

2 is outside the interval for which asin is defined. Pythons math.asin is an implemetation of arc sine and thus it is defined for values between -1.0 and 1.0

[jahuja73]

2 is outside the interval for which asin is defined. Pythons math.asin is an implemetation of arc sine and thus it is defined for values between -1.0 and 1.0

Agreed, but took it from a SO post on computing square roots using trigonometry, at : https://stackoverflow.com/a/17410692/3693431.

The code is not in python, but on translation it should be:

n = 5; #number to get the square root of

icr = ((n+1)/2); #intersecting circle radius

sqrt = Math.cos(Math.asin((icr-1)/icr))*icr; /#square root of n

I hope though the code is not in python, should behave same.

Even the working principle wasn't (and still is not) clear.
To understand that, wanted to put prints; but it gave error straight away; leading to this question.

[bowlofred]

That function will work because for most inputs, the argument to math.asin will be between 0 and 1. If you printed out the variables there it should work fine.