# How do you write the complex number in trigonometric form 3i?

the trigonometric form is $3 \left(\cos \left(\frac{\pi}{2}\right) + i \sin \left(\frac{\pi}{2}\right)\right)$
so, $\cos \theta = 0$ and $\sin \theta = 1$
So $\theta = \frac{\pi}{2}$
So the trigonometric form is $3 \left(\cos \left(\frac{\pi}{2}\right) + i \sin \left(\frac{\pi}{2}\right)\right)$
and you can also write it as $3 {e}^{i \frac{\pi}{2}}$