# Thread: complex numbers questions help

1. ## complex numbers questions help

I have coursework to do and I really want a good mark. This question that i am doing is not giving me nice numbers at the end, so if anyone can tell me what they get to make sure I'm not doing it wrong.

Q1 Let z = 3+5i and w = 3e^[(3*pi)/4] (w= 3 times e to the power of everything in square brackets)

Find:
1)z*w
2)z/w
3)z+w

thanks so much for any help

2. Originally Posted by princessamme@hotmail.com
I have coursework to do and I really want a good mark. This question that i am doing is not giving me nice numbers at the end, so if anyone can tell me what they get to make sure I'm not doing it wrong.

Q1 Let z = 3+5i and w = 3e^[(3*pi)/4] (w= 3 times e to the power of everything in square brackets)

Find:
1)z*w
2)z/w
3)z+w

thanks so much for any help
Let me guess

w=3e^[(3i pi)/4]

Just use the fact that

e^{ix}=cos(x)+i*sin(x)

EDIT:

3. wups ye you were right i did mean 3*pi*i. i did that and got
w= [(-3*root2)/2] + [i*(3*root2)/2]. is this right? it makes the final answers quite complicated numbers, especially part 3 (z+w)

4. I think the answer is
z*w=-3*root2*(4+i)
z/w=-root2/3*(1-4i)
z+w=3-3*root2/2+(3*root2/2+5)i

5. Thanks, yeah thoses were the answers i got i just thought they were funny numbers so was just checking