The complex number - 5i has the complex trigonometric form of 5 (cos 270° + isin 270)

True, - 5i = 5 * (0 - i) = 5 * (cos 3π/2 + i*sin 3π/2) = 5 * (cos 270 + i*sin 270)

Step-by-step explanation:

5 * (cos 3π/2 radians + i*sin 3π/2 radians) = 5 * (cos 270 degrees + i*sin 270 degrees)