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Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

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Appendix I / Utilities / Trigonometrical Functions<br />

_ _<br />

ACOS_F AND ASIN_F ERRORS (DEGREES)<br />

0.15<br />

0.1<br />

0.05<br />

0<br />

-0.05<br />

-0.1<br />

ASIN_F (SOLID)<br />

ACOS_F (DASHED)<br />

0 0.2 0.4 0.6 0.8 1<br />

Figure 22-13 : Arc-Sine and Cosine Function Errors<br />

The error in this function is the same as that for arc-sine but in anti-phase as<br />

shown in Figure 22-13.<br />

22.11.6 Arc-tangent Approximation (Single Argument)<br />

ATAN_F takes the tangent of (XI), and returns (XI) in the range<br />

]-π/2 , π/2[ .<br />

y<br />

: = ATAN_F<br />

( X )<br />

I<br />

22.11-5<br />

: =<br />

0.<br />

6287<br />

1.<br />

5708 ⋅ X<br />

+<br />

I<br />

0.<br />

8822<br />

+ X<br />

2<br />

I<br />

Equation 22.11-18<br />

The error in this function is [-0.04°, 0.04°] over the range [0 , 15] as shown<br />

in Figure 22-14.<br />

22.11.7 Arc-tangent Approximation (Two Arguments)<br />

ATAN2_F takes in (YI) and (XI) and returns an angle in the range ]-π , π[ .<br />

: y ATAN2_F<br />

=<br />

( ) , Y<br />

I I X<br />

Equation 22.11-19<br />

−15<br />

−15<br />

−1<br />

( < 10 ) ∧ ( Y < 10 ) ⇒ y : = tan ( Y X ) : = 0<br />

XI I<br />

I I<br />

I<br />

( 1,<br />

ξ1<br />

) − 1<br />

X < 0 ⇒ y : = 2 ⋅ sign ξ<br />

Equation 22.11-20<br />

Equation 22.11-21

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