25 lines
520 B
Go
25 lines
520 B
Go
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package bloob
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import "math"
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func FastSin(x float64) float64 {
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const PI = 3.14159265358979323846264338327950288
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const INVPI = 0.31830988618379067153776752674502872
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const A = 0.00735246819687011731341356165096815
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const B = -0.16528911397014738207016302002888890
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const C = 0.99969198629596757779830113868360584
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k := int32(math.Round(INVPI * x))
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x -= float64(k) * PI
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x2 := x * x
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x = x * (C + x2*(B+A*x2))
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if k%2 != 0 {
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x = -x
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}
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return x
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}
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func FastCos(x float64) float64 {
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return FastSin(x + math.Pi/2)
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}
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