trigonometry.h File Reference

Detailed Description

Design Philosophy

Floating point or double precision trigonometry is slow. Look up tables are fast! These functions do a good job approximating sine, cosine, and tangent.

The arguments are in degrees, not radians, and they return (1024 * the trigonometric function).

Usage

Call getSin1024(), getCos1024(), or getTan1024() with a degree between 0 and 359 inclusive. If the input degree is out of bounds, the result will be indeterminate.

The sin1024 and tan1024 arrays contain the first 91 elements of the respective functions and can be used directly if you're careful.

Example

printf("%d\n", getSin1024(180));

Go to the source code of this file.

Functions
int16_t	getSin1024 (int16_t degree)
int16_t	getCos1024 (int16_t degree)
int32_t	getTan1024 (int16_t degree)
int32_t	cordicAtan2 (int32_t x, int32_t y)
	CORDIC approximation of arctan.
int16_t	getAtan2 (int32_t y, int32_t x)
	Calculate the angle of the line from the origin to (x, y), in degrees.

Variables
const int16_t	sin1024 [91]
const uint16_t	tan1024 [91]

Function Documentation

getSin1024()

int16_t getSin1024

(

int16_t

degree

)

Integer sine function

Parameters

degree

The degree, between 0 and 359

Returns

The sine of the degree, between -1024 and 1024

getCos1024()

int16_t getCos1024

(

int16_t

degree

)

Integer cosine function

Parameters

degree

The degree, between 0 and 359

Returns

The cosine of the degree, between -1024 and 1024

getTan1024()

int32_t getTan1024

(

int16_t

degree

)

Integer tangent function

Parameters

degree

The degree, between 0 and 359

Returns

The tangent of the degree, scaled by 1024

cordicAtan2()

int32_t cordicAtan2	(	int32_t	x,
		int32_t	y )

CORDIC approximation of arctan.

Parameters

x	The x component
y	The y component

Returns

The approximation of atan(y/x), in degrees

getAtan2()

int16_t getAtan2	(	int32_t	y,
		int32_t	x )

Calculate the angle of the line from the origin to (x, y), in degrees.

If both x and y are 0, atan2 is undefined and will return 0.

Parameters

y	The Y coordinate of the point to calculate the angle to
x	The X coordinate of the point to calculate the angle to

Returns

int16_t The angle degree, between 0 and 359.

Variable Documentation

sin1024

const int16_t sin1024[91]

extern

A table of the first 91 values of (1024 * sin(x)). Only 91 values are necessary because getSin1024() and getCos1024() handle symmetry to calculate the full wave

tan1024

const uint16_t tan1024[91]

extern

A table of the first 91 values of (1024 * tan(x)). Only 91 values are necessary because getTan1024() handles symmetry to calculate the full wave