Question

Convert the following polar representation of this complex number into it's regular form: z=4(cos pi/2+isinpi/2)?
A.(0,4)
B.(-4,0)
C.(4sqrt2,0)
D.(0,-4)

Answer 1

The question seems a bit strange as currently worded... The answer choices don't match up... since the complex number is ALREADY in polar representation... :)

Answer 2

ill double check the question

Answer 3

@jtvatsim fixed it:)

Answer 4

That makes more sense... but now let's see if I can figure out the real question. :P lol

Answer 5

Alright, so for these you need to either have memorized what cos(pi/2) and sin(pi/2) are, use a calculator (in radians mode), or use the unit circle. :)

Answer 6

I happen to see these a lot, so I can tell you that cos(pi/2) = 0 and sin(pi/2) = 1.

Answer 7

OK so far?

Answer 8

yeah

Answer 9

Alright, so now we just simplify the given number:

z = 4(cos pi/2 + i sin pi/2)
= 4(0 + i * 1)
= 4( i )
= 4i.

Answer 10

If you are feeling really "textbook mathy" this is the same as 4i = 0 + 4i or some people write it like a coordinate (0, 4) where it is understood that the first coordinate gives the "real" number values, and the second coordinate gives the "imaginary" i values.

Answer 11

so in order to get the answer that's all you do?

Answer 12

Yes, converting from polar form to regular form is much easier than going the other direction.

Answer 13

Thanks:) So the final amswer is A. (0,4

Answer 14

No problem! You are good to go!