1 files changed, 40 insertions, 0 deletions
diff --git a/src/base/math/asin.c b/src/base/math/asin.c
new file mode 100644
index 0000000..4687715
--- /dev/null
+++ b/src/base/math/asin.c
@@ -0,0 +1,40 @@
+/*
+ * asin(arg) and acos(arg) return the arcsin, arccos,
+ * respectively of their arguments.
+ *
+ * Arctan is called after appropriate range reduction.
+ */
+
+#include <u.h>
+#include <base.h>
+
+double
+math·asin(double arg)
+{
+	double temp;
+	int sign;
+
+	sign = 0;
+	if(arg < 0) {
+		arg = -arg;
+		sign++;
+	}
+	if(arg > 1)
+		return math·NaN();
+	temp = math·sqrt(1 - arg*arg);
+	if(arg > 0.7)
+		temp = math·PIO2 - math·atan(temp/arg);
+	else
+		temp = math·atan(arg/temp);
+	if(sign)
+		temp = -temp;
+	return temp;
+}
+
+double
+math·acos(double arg)
+{
+	if(arg > 1 || arg < -1)
+		return math·NaN();
+	return math·PIO2 - math·asin(arg);
+}