CosineFast Math Functions

Functions

float32_t arm_cos_f32 (float32_t x)
 Fast approximation to the trigonometric cosine function for floating-point data.
 
q15_t arm_cos_q15 (q15_t x)
 Fast approximation to the trigonometric cosine function for Q15 data.
 
q31_t arm_cos_q31 (q31_t x)
 Fast approximation to the trigonometric cosine function for Q31 data.
 

Description

Computes the trigonometric cosine function using a combination of table lookup and linear interpolation. There are separate functions for Q15, Q31, and floating-point data types. The input to the floating-point version is in radians and in the range [0 2*pi) while the fixed-point Q15 and Q31 have a scaled input with the range [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a value of 2*pi wraps around to 0.

The implementation is based on table lookup using 256 values together with linear interpolation. The steps used are:

  1. Calculation of the nearest integer table index
  2. Compute the fractional portion (fract) of the table index.
  3. The final result equals (1.0f-fract)*a + fract*b;

where

   b=Table[index+0];
   c=Table[index+1];

Function Documentation

float32_t arm_cos_f32 ( float32_t  x)
Parameters
[in]xinput value in radians.
Returns
cos(x).

References FAST_MATH_TABLE_SIZE, and sinTable_f32.

Referenced by main().

q15_t arm_cos_q15 ( q15_t  x)
Parameters
[in]xScaled input value in radians.
Returns
cos(x).

The Q15 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi).

References FAST_MATH_Q15_SHIFT, and sinTable_q15.

q31_t arm_cos_q31 ( q31_t  x)
Parameters
[in]xScaled input value in radians.
Returns
cos(x).

The Q31 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi).

References FAST_MATH_Q31_SHIFT, and sinTable_q31.