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 Cosine CMSIS-DSP: Cosine
CMSIS-DSP  Version 1.4.7
CMSIS DSP Software Library

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 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
Returns
cos(x).
Examples:
arm_sin_cos_example_f32.c.

References FAST_MATH_TABLE_SIZE, and sinTable_f32.

Referenced by main().

q15_t arm_cos_q15 ( q15_t  x)
Parameters
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