float hypotf(float x, float y);

**hypotf** computes the square root of the sum of the squares of
**x** and **y**, **sqrtf**(**x*****x** + **y*****y**), without undue overflow or underflow.
If **x** and **y** are the lengths of the sides of a right-angled triangle,
then **hypotf** computes the length of the hypotenuse.

If **x** or **y** is +∞ or ?∞, **hypotf** returns ∞.
If **x** or **y** is NaN, **hypotf** returns NaN.