B = sqrt(X)returns the square root of each element of the arrayX. For the elements ofXthat are negative or complex,sqrt(X)produces complex results.

Thesqrtfunction’s domain includes negative and complex numbers, which can lead to unexpected results if used unintentionally. For negative and complex numbersz = u + i*w,复杂的平方根sqrt(z)returns

sqrt(r)*(cos(phi/2) + 1i*sin(phi/2))

wherer = abs(z)is the radius andphi = angle(z)is the phase angle on the closed interval-pi <= phi <= pi.

If you want negative and complex numbers to return error messages rather than return complex results, userealsqrtinstead.