/
arctan.c
103 lines (85 loc) · 1.4 KB
/
arctan.c
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#include "stdafx.h"
#include "defs.h"
void
eval_arctan(void)
{
push(cadr(p1));
eval();
arctan();
}
void
arctan(void)
{
double d;
save();
p1 = pop();
if (car(p1) == symbol(TAN)) {
push(cadr(p1));
restore();
return;
}
if (isdouble(p1)) {
errno = 0;
d = atan(p1->u.d);
if (errno)
stop("arctan function error");
push_double(d);
restore();
return;
}
if (iszero(p1)) {
push(zero);
restore();
return;
}
if (isnegative(p1)) {
push(p1);
negate();
arctan();
negate();
restore();
return;
}
// arctan(sin(a) / cos(a)) ?
if (find(p1, symbol(SIN)) && find(p1, symbol(COS))) {
push(p1);
numerator();
p2 = pop();
push(p1);
denominator();
p3 = pop();
if (car(p2) == symbol(SIN) && car(p3) == symbol(COS) && equal(cadr(p2), cadr(p3))) {
push(cadr(p2));
restore();
return;
}
}
// arctan(1/sqrt(3)) -> pi/6
if (car(p1) == symbol(POWER) && equaln(cadr(p1), 3) && equalq(caddr(p1), -1, 2)) {
push_rational(1, 6);
push(symbol(PI));
multiply();
restore();
return;
}
// arctan(1) -> pi/4
if (equaln(p1, 1)) {
push_rational(1, 4);
push(symbol(PI));
multiply();
restore();
return;
}
// arctan(sqrt(3)) -> pi/3
if (car(p1) == symbol(POWER) && equaln(cadr(p1), 3) && equalq(caddr(p1), 1, 2)) {
push_rational(1, 3);
push(symbol(PI));
multiply();
restore();
return;
}
push_symbol(ARCTAN);
push(p1);
list(2);
restore();
}