Update

sqrt.md

@@ -141,6 +141,24 @@ int32_t sqrtApprox(int32_t x)
 }
 ```
 
+If we need [floating point](float.md) square root, we can very well use [numerical methods](numerical.md): for example wanting to find square root of *a* we may apply Newton's method to arrive at the formula:
+
+*x[n + 1] = 1/2 * (x[n] + a / x[n])*
+
+into which we may substitute the initial estimate as *x[0]* and then just keep evaluating the series until the error becomes small enough. Here this is implemented in C (to keep it simple performing a fixed number of iterations that showed to give accurate results even for high values):
+
+```
+double sqrtF(double x)
+{
+  double r = x / 2 + 1;
+
+  for (int i = 0; i < 20; ++i)
+    r = 0.5 * (r + x / r);
+
+  return r;
+}
+```
+
 ## See Also
 
 - [logarithm](log.md)