JeffCoderr - 1 year ago 147
C++ Question

# sin & cos funcs without math.h

I cannot use the c++ functions

`sin()`
and
`cos()`
due to certain compiler issues caused by PS3 3.40 SDK. What are the calculations of
`sin()`
&
`cos()`
so i can use functions without needing
`math.h`
?

I have so far came up with these, but they seem to not be functioning correctly?

``````float sin(float deg) {
bool neg = false;
while (deg >= 360) deg = deg - 360;
while (deg < 0) deg = deg + 360;
if (deg > 180) {
deg = deg - 180;
neg = true;
}
float ret = (float)(4*deg*(180-deg))/(40500-(deg*(180-deg)));
if (neg)return ret*-1;
return ret;
}

float cos(float AnglesDeg)
{
return sin(ang);
}
``````

You can use Taylor Series to implement this by yourself. The code is straight forward:

``````float sine(int deg) {
deg %= 360; // make it less than 360
float rad = deg * PI / 180;
float sin = 0;

int i;
for(i = 0; i < TERMS; i++) { // That's Taylor series!!
sin += power(-1, i) * power(rad, 2 * i + 1) / fact(2 * i + 1);
}
return sin;
}

float cosine(int deg) {
deg %= 360; // make it less than 360
float rad = deg * PI / 180;
float cos = 0;

int i;
for(i = 0; i < TERMS; i++) { // That's also Taylor series!!
cos += power(-1, i) * power(rad, 2 * i) / fact(2 * i);
}
return cos;
}
``````

As you said you don't have math.h, I made a simple power function for this algorithm. Also you need a function to calculate factorial nubmers. Here they are:

``````float power(float base, int exp) {
if(exp < 0) {
if(base == 0)
return -0; // Error!!
return 1 / (base * power(base, (-exp) - 1));
}
if(exp == 0)
return 1;
if(exp == 1)
return base;
return base * power(base, exp - 1);
}

int fact(int n) {
return n <= 0 ? 1 : n * fact(n-1);
}
``````

PI and TERMS were just preprocessor directives (`#define`'s) I used, being PI 3.14159 (in my case I used a 50 digits precision pi, what is completely unnecessary) and TERMS being 7.

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