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diff --git a/vendor/libm-0.1.4/src/math/atan2.rs b/vendor/libm-0.1.4/src/math/atan2.rs
new file mode 100644
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+++ b/vendor/libm-0.1.4/src/math/atan2.rs
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+/* origin: FreeBSD /usr/src/lib/msun/src/e_atan2.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ *
+ */
+/* atan2(y,x)
+ * Method :
+ *      1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
+ *      2. Reduce x to positive by (if x and y are unexceptional):
+ *              ARG (x+iy) = arctan(y/x)           ... if x > 0,
+ *              ARG (x+iy) = pi - arctan[y/(-x)]   ... if x < 0,
+ *
+ * Special cases:
+ *
+ *      ATAN2((anything), NaN ) is NaN;
+ *      ATAN2(NAN , (anything) ) is NaN;
+ *      ATAN2(+-0, +(anything but NaN)) is +-0  ;
+ *      ATAN2(+-0, -(anything but NaN)) is +-pi ;
+ *      ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2;
+ *      ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
+ *      ATAN2(+-(anything but INF and NaN), -INF) is +-pi;
+ *      ATAN2(+-INF,+INF ) is +-pi/4 ;
+ *      ATAN2(+-INF,-INF ) is +-3pi/4;
+ *      ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2;
+ *
+ * Constants:
+ * The hexadecimal values are the intended ones for the following
+ * constants. The decimal values may be used, provided that the
+ * compiler will convert from decimal to binary accurately enough
+ * to produce the hexadecimal values shown.
+ */
+
+use super::atan;
+use super::fabs;
+
+const PI: f64 = 3.1415926535897931160E+00; /* 0x400921FB, 0x54442D18 */
+const PI_LO: f64 = 1.2246467991473531772E-16; /* 0x3CA1A626, 0x33145C07 */
+
+/// Arctangent of y/x (f64)
+///
+/// Computes the inverse tangent (arc tangent) of `y/x`.
+/// Produces the correct result even for angles near pi/2 or -pi/2 (that is, when `x` is near 0).
+/// Returns a value in radians, in the range of -pi to pi.
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn atan2(y: f64, x: f64) -> f64 {
+    if x.is_nan() || y.is_nan() {
+        return x + y;
+    }
+    let mut ix = (x.to_bits() >> 32) as u32;
+    let lx = x.to_bits() as u32;
+    let mut iy = (y.to_bits() >> 32) as u32;
+    let ly = y.to_bits() as u32;
+    if ((ix.wrapping_sub(0x3ff00000)) | lx) == 0 {
+        /* x = 1.0 */
+        return atan(y);
+    }
+    let m = ((iy >> 31) & 1) | ((ix >> 30) & 2); /* 2*sign(x)+sign(y) */
+    ix &= 0x7fffffff;
+    iy &= 0x7fffffff;
+
+    /* when y = 0 */
+    if (iy | ly) == 0 {
+        return match m {
+            0 | 1 => y, /* atan(+-0,+anything)=+-0 */
+            2 => PI,    /* atan(+0,-anything) = PI */
+            _ => -PI,   /* atan(-0,-anything) =-PI */
+        };
+    }
+    /* when x = 0 */
+    if (ix | lx) == 0 {
+        return if m & 1 != 0 { -PI / 2.0 } else { PI / 2.0 };
+    }
+    /* when x is INF */
+    if ix == 0x7ff00000 {
+        if iy == 0x7ff00000 {
+            return match m {
+                0 => PI / 4.0,        /* atan(+INF,+INF) */
+                1 => -PI / 4.0,       /* atan(-INF,+INF) */
+                2 => 3.0 * PI / 4.0,  /* atan(+INF,-INF) */
+                _ => -3.0 * PI / 4.0, /* atan(-INF,-INF) */
+            };
+        } else {
+            return match m {
+                0 => 0.0,  /* atan(+...,+INF) */
+                1 => -0.0, /* atan(-...,+INF) */
+                2 => PI,   /* atan(+...,-INF) */
+                _ => -PI,  /* atan(-...,-INF) */
+            };
+        }
+    }
+    /* |y/x| > 0x1p64 */
+    if ix.wrapping_add(64 << 20) < iy || iy == 0x7ff00000 {
+        return if m & 1 != 0 { -PI / 2.0 } else { PI / 2.0 };
+    }
+
+    /* z = atan(|y/x|) without spurious underflow */
+    let z = if (m & 2 != 0) && iy.wrapping_add(64 << 20) < ix {
+        /* |y/x| < 0x1p-64, x<0 */
+        0.0
+    } else {
+        atan(fabs(y / x))
+    };
+    match m {
+        0 => z,                /* atan(+,+) */
+        1 => -z,               /* atan(-,+) */
+        2 => PI - (z - PI_LO), /* atan(+,-) */
+        _ => (z - PI_LO) - PI, /* atan(-,-) */
+    }
+}
+
+#[test]
+fn sanity_check() {
+    assert_eq!(atan2(0.0, 1.0), 0.0);
+    assert_eq!(atan2(0.0, -1.0), PI);
+    assert_eq!(atan2(-0.0, -1.0), -PI);
+    assert_eq!(atan2(3.0, 2.0), atan(3.0 / 2.0));
+    assert_eq!(atan2(2.0, -1.0), atan(2.0 / -1.0) + PI);
+    assert_eq!(atan2(-2.0, -1.0), atan(-2.0 / -1.0) - PI);
+}