1 use super::{log1pf, logf, sqrtf};
2
3 const LN2: f32 = 0.693147180559945309417232121458176568;
4
5 /// Inverse hyperbolic cosine (f32)
6 ///
7 /// Calculates the inverse hyperbolic cosine of `x`.
8 /// Is defined as `log(x + sqrt(x*x-1))`.
9 /// `x` must be a number greater than or equal to 1.
acoshf(x: f32) -> f3210 pub fn acoshf(x: f32) -> f32 {
11 let u = x.to_bits();
12 let a = u & 0x7fffffff;
13
14 if a < 0x3f800000 + (1 << 23) {
15 /* |x| < 2, invalid if x < 1 or nan */
16 /* up to 2ulp error in [1,1.125] */
17 return log1pf(x - 1.0 + sqrtf((x - 1.0) * (x - 1.0) + 2.0 * (x - 1.0)));
18 }
19 if a < 0x3f800000 + (12 << 23) {
20 /* |x| < 0x1p12 */
21 return logf(2.0 * x - 1.0 / (x + sqrtf(x * x - 1.0)));
22 }
23 /* x >= 0x1p12 */
24 return logf(x) + LN2;
25 }
26