We calculate the module:
[tex]|z|\: = \: \sqrt{( - 3) ^{2} \: + \: {4}^{2} } [/tex]
[tex]|z| \: = \: \sqrt{9 \: + \: 16} [/tex]
[tex]|z| \: = \: \sqrt{25} [/tex]
[tex] \boxed{|z| \: = \: 5}[/tex]
We calculate the angle formed by "z":
[tex] \arctan( \frac{4}{ - 3} ) \: = \: \underline{0.92729521 \: \text{rad}}[/tex]
We pass it to degrees:
[tex]0.92729521 \: \times \: \frac{180}{\pi} [/tex]
[tex] \frac{166.91313924}{\pi} [/tex]
[tex] \frac{166.91313924}{3.14159265}[/tex]
[tex] \boxed{ 53.13°}[/tex]
Now we use this formula to transform it into a trigonometric form:
[tex] \boxed{z \: = \: |z| \times \: ( \cos( \alpha) \: + \: i \: \times \: \sin( \alpha))}[/tex]
[tex] \boxed{ \bold{z \: = \: 5 \times \: ( \cos( 53.13°) \: + \: i \: \times \: \sin( 53.13°))}}[/tex]
[tex] \boxed{ \bold{z \: = \: 5 \times \: ( \cos( 53.13°) \: + \: i \: \times \: \sin( 53.13°))}}[/tex]