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Cosine is symmetric, sine is antisymmetric.

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This commit is contained in:
George Weigt 2004-06-19 10:34:47 -07:00
parent e3091ccc0a
commit 6c2ff199a1
4 changed files with 63 additions and 26 deletions

29
cos.cpp
View file

@ -43,6 +43,14 @@ cosine_f(void)
return;
}
// cosine function is symmetric, cos(-x) = cos(x)
if (isnegative(p1)) {
push(p1);
negate();
p1 = pop();
}
// multiply by 180/pi
push(p1);
@ -53,16 +61,13 @@ cosine_f(void)
n = pop_integer();
if (n == (int) 0x80000000) {
if (n < 0) {
push_symbol(COS);
push(p1);
list(2);
return;
}
if (n < 0)
n = -n;
switch (n % 360) {
case 0:
push_integer(1);
@ -105,10 +110,10 @@ static char *s[] = {
"-1",
"cos(-5/6*pi)", // -150 degrees
"cos(-5/6*pi)",
"cos(5/6*pi)",
"cos(-3/4*pi)", // -135 degrees
"cos(-3/4*pi)",
"cos(3/4*pi)",
"cos(-pi*2/3)", // -120 degrees
"-1/2",
@ -120,10 +125,10 @@ static char *s[] = {
"1/2",
"cos(-1/4*pi)", // -45 degrees
"cos(-1/4*pi)",
"cos(1/4*pi)",
"cos(-1/6*pi)", // -30 degrees
"cos(-1/6*pi)",
"cos(1/6*pi)",
"cos(0)", // 0 degrees
"1",
@ -160,6 +165,14 @@ static char *s[] = {
"expomode=0",
"",
// cosine function is symmetric
"cos(-x)",
"cos(x)",
"cos(b-a)",
"cos(a-b)",
};
void

1
defs.h
View file

@ -368,6 +368,7 @@ void gmp_collect(void);
void denominator(void);
void rationalize(void);
int isnegativenumber(U *);
int isnegative(U *);
void test_gcd(void);
void factor(void);
void test_factor(void);

11
is.cpp
View file

@ -202,3 +202,14 @@ iseveninteger(U *p)
else
return 0;
}
int
isnegative(U *p)
{
if (car(p) == symbol(ADD) && isnegativeterm(cadr(p)))
return 1;
else if (isnegativeterm(p))
return 1;
else
return 0;
}

48
sin.cpp
View file

@ -24,7 +24,7 @@ sine(void)
static void
sine_f(void)
{
int n, u;
int n;
double d;
p1 = pop();
@ -43,6 +43,16 @@ sine_f(void)
return;
}
// sine function is antisymmetric, sin(-x) = -sin(x)
if (isnegative(p1)) {
push(p1);
negate();
sine();
negate();
return;
}
// multiply by 180/pi
push(p1);
@ -53,43 +63,37 @@ sine_f(void)
n = pop_integer();
if (n == (int) 0x80000000) {
if (n < 0) {
push_symbol(SIN);
push(p1);
list(2);
return;
}
if (n < 0) {
n = -n;
u = -1;
} else
u = 1;
switch (n % 360) {
case 0:
push_integer(0);
break;
case 30:
push_rational(u, 2);
push_rational(1, 2);
break;
case 90:
push_integer(u);
push_integer(1);
break;
case 150:
push_rational(u, 2);
push_rational(1, 2);
break;
case 180:
push_integer(0);
break;
case 210:
push_rational(-u, 2);
push_rational(-1, 2);
break;
case 270:
push_integer(-u);
push_integer(-1);
break;
case 330:
push_rational(-u, 2);
push_rational(-1, 2);
break;
default:
push_symbol(SIN);
@ -111,19 +115,19 @@ static char *s[] = {
"-1/2",
"sin(-3/4*pi)", // -135 degrees
"sin(-3/4*pi)",
"-sin(3/4*pi)",
"sin(-2/3*pi)", // -120 degrees
"sin(-2/3*pi)",
"-sin(2/3*pi)",
"sin(-pi/2)", // -90 degrees
"-1",
"sin(-1/3*pi)", // -60 degrees
"sin(-1/3*pi)",
"-sin(1/3*pi)",
"sin(-1/4*pi)", // -45 degrees
"sin(-1/4*pi)",
"-sin(1/4*pi)",
"sin(-pi/6)", // -30 degrees
"-1/2",
@ -166,6 +170,14 @@ static char *s[] = {
"expomode=0",
"",
// sine function is antisymmetric
"sin(-x)",
"-sin(x)",
"sin(b-a)",
"-sin(a-b)",
};
void