Question

How do you express the complex number in trigonometric form `3(cos 90° + i sin 90°)`?

Answer 1

Your number, which is in trigonometric form, can be expressed in standard or rectangular form, `z=a+ib`, considering that:
`cos(90°)=0`
`sin(90°)=1`
Giving you:
`z=3(0+1i)=3i` a pure immaginary.