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Embedded Software and Motor Control Libraries for PXR40xx

Embedded Software and Motor Control Libraries for PXR40xx

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Function GFLIB_Acos_F32<br />

4.25 Function GFLIB_Acos_F32<br />

This function implements polynomial approximation of arccosine function.<br />

4.25.1 Declaration<br />

tFrac32 GFLIB_Acos_F32(tFrac32 f32In, const GFLIB_ACOS_T_F32 *const pParam);<br />

4.25.2 Arguments<br />

Table 4-25. GFLIB_Acos_F32 arguments<br />

Type Name Direction Description<br />

tFrac32 f32In input Input argument is a 32-bit number that contains a value<br />

between [-1,1).<br />

const<br />

GFLIB_ACOS_T_F32<br />

*const<br />

4.25.3 Return<br />

pParam input Pointer to an array of Taylor coefficients.<br />

The function returns arccos(f32In)/ π as a fixed point 32-bit number, normalized between<br />

[0,1).<br />

4.25.4 Description<br />

The GFLIB_Acos_F32 function provides a computational method <strong>for</strong> calculation of the<br />

st<strong>and</strong>ard inverse trigonometric arccosine function arccos(x), using the piece-wise<br />

polynomial approximation. Function arccos(x) takes the ratio of the length of the adjacent<br />

side to the length of the hypotenuse <strong>and</strong> returns the angle.<br />

<strong>Embedded</strong> <strong>Software</strong> <strong>and</strong> <strong>Motor</strong> <strong>Control</strong> <strong>Libraries</strong> <strong>for</strong> <strong>PXR40xx</strong>, Rev. 1.0<br />

208 Freescale Semiconductor, Inc.

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