require 'bigdecimal'
require 'bigdecimal/math'
include BigMath
Math::PI # => 3.14159265358979
Math::PI.class # => Float
BigDecimal.PI(1).to_s
# => "0.31415926535897932364198143965603E1"
BigDecimal.PI(20).to_s
# => "0.3141592653589793238462643383279502883919859293521427E1"