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)

b. 1.25 hr

step-by-step explanation:

if you have a constant speed of 60 mph, then you have a ratio between 60 mi. to 1 hr. dividing both sides by 60 we get the ratio

1 mi. to

then mult. both sides by 75 we get the ratio

75 mi. to

simplifying we get

75 mi. to

or 1.25 hr.