more trigonomic functions and definitions

trig.c

pi=4*a(1)
d=pi/180

define sin(x){return s(x)}
define cos(x){return c(x)}
define atan(x){return a(x)}

define tan(x) {
  if (c(x)==0) return pi/2
  return s(x)/c(x)
}

define acos(x) {
  if (x==0) return pi/2
  return a(sqrt(1/x^2-1))
}

define asin(x) {
  if (x==1) return pi/2
  return a(sqrt(1/(1-x^2)-1))
}

pi@pi400-64:~ $ bc -ql trig.bc
sin(60*d)
.86602540378443864648
cos(60*d)
.50000000000000000047
tan(45*d)
.99999999999999999916
atan(1)/d
45.00000000000000002349
asin(sqrt(3)/2)/d
60.00000000000000003093
acos(0.5)/d
60.00000000000000003151