Upvoted for calc. I use it for all the small calculation, as it most often behaves slightly better than bc

  $ echo "1/2" | bc
  0

  $ echo "1/2" | bc -l
  .50000000000000000000

  $ echo "scale=1; 1/2" | bc
  .5

  $ echo "1/2" | calc -p
  0.5

  $ echo "+1+1+1+1" | bc -l
  (standard_in) 1: syntax error

  $ echo "+1+1+1+1" | calc -p
  4

  $ echo "sqrt(-1)" | bc -l
  Runtime error (func=(main), adr=4): Square root of a negative number

  $ echo "sqrt(-1)" | calc -p
  1i

  $ echo "s(pi)" | bc -l
  0

  $ echo "sin(pi())" | calc -p
  0