pub fn half_pi<T: RealNumber>() -> T
Returns pi / 2.
pi / 2
four_over_pi()
one_over_pi()
one_over_two_pi()
pi()
quarter_pi()
root_half_pi()
root_pi()
root_two_pi()
three_over_two_pi()
two_over_pi()
two_over_root_pi()
two_pi()