How do you express the complex number in trigonometric form # 2(cos 90° + i sin 90°)#?
In a sense, it's already in trigonometric form. Other common ways to write it, which may be what you are after, are
The second form follows from Euler's formula:
The "cis" form of the answer is just another way to write it (
All of this can also be thought of in terms of polar coordinates in the complex plane. The polar coordinates of the complex number