CMSIS-DSP: Cosine

| CMSIS-DSP Version 1.5.2 CMSIS DSP Software Library

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Cosine
Fast Math Functions

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

## 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 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] | x | input 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] | x | Scaled 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] | x | Scaled 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.