add hypot

base/usr/include/math.h

@@ -30,3 +30,5 @@ extern double tanh(double x);
 extern double atan(double x);
 
 extern double modf(double x, double *iptr);
+
+extern double hypot(double x, double y);

libc/math/math.c

@@ -458,3 +458,6 @@ double atan2(double y, double x) {
 	return out;
 }
 
+double hypot(double x, double y) {
+	return sqrt(x * x + y * y);
+}