To calculate i in complex numbers, you can start by finding the imaginary part. To do so, follow the next steps.
Identify the form of your complex number:
a. If the number is in the form a + bi, go to step 2.
b. If the number is in the form |z|eiφ, go to step 3.
Take the imaginary part bi and remove the complex root i. The result is b.
Follow the next two steps:
Compute the sine of the phase φ, sin(φ).
Multiply it by the modulo |z|: the result is |z|sin(φ).