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.