





from math import pi






def 				__lowerCamelCase		(						lowerCAmelCase__     ,  lowerCAmelCase__     ):
       return 2 * pi * radius * (angle / 3_6_0)


if __name__ == "__main__":
    print(arc_length(90, 10))

from math import log

from scipy.constants import Boltzmann, physical_constants

lowerCAmelCase__     						=			300  # TEMPERATURE (unit = K)






def 				__lowerCamelCase		(						lowerCAmelCase__     ,  lowerCAmelCase__     ,  lowerCAmelCase__     ,  ):

       if donor_conc <= 0:
              raise ValueError('Donor concentration should be positive'     )
       elif acceptor_conc <= 0:
              raise ValueError('Acceptor concentration should be positive'     )
       elif intrinsic_conc <= 0:
              raise ValueError('Intrinsic concentration should be positive'     )
       elif donor_conc <= intrinsic_conc:
              raise ValueError(
                  'Donor concentration should be greater than intrinsic concentration'     )
       elif acceptor_conc <= intrinsic_conc:
              raise ValueError(
                  'Acceptor concentration should be greater than intrinsic concentration'     )
       else:
              return (
                  Boltzmann
                  * T
                  * log((donor_conc * acceptor_conc) / intrinsic_conc**2     )
                  / physical_constants["electron volt"][0]
              )


if __name__ == "__main__":
    import doctest

    doctest.testmod()
