angle() further help

I am trying to use the angle function in order to calculate the angle of complex numbers. I have been trying to understand how the angles of complex co-ordinates in the 3rd quadrant are calculated? The example I have been using is z= -2 - 5i, the angle function (and rad2deg()) gives an answer of -111.8014. I don't understand where this figure comes from, can anyone shed some light on this?

Answer 1

[KSSV]

angle gives you the value of inverse tan of imaginary values divided real value.

z= -2 - 5*1i ;
 atan(imag(z)/real(z))

[Rik]

To avoid confusion: the imaginary and real parts. In this case that would be

atan( (-5) ./ (-2) )

Thanks for spotting my mistake Adam ;)

[Adam]

Or

atan( (-5) ./ (-2) )

to avoid confusion in the clearing up of the confusion :-)