Question

Ex

Answer 1

did you plot the point (-4+0i)

plot (-4,0) on the complex plane
(this is the same problem you posted in physics... see the picture there)

Answer 2

@agent0smith @jim_thompson5910

Answer 3

As @phi wrote, think of -4 as -4+0i

Answer 4

this will plot at (-4,0)

how can we write (-4,0) in (r,theta) form?

Answer 5

\[\Large r = \sqrt{x^2+y^2}\]
\[\Large \theta = \arctan\left(\frac{y}{x}\right)\]
In this case, x = -4 and y = 0

Answer 6

@jim_thompson5910

Answer 7

were you able to find the value of 'r'?

Answer 8

Plug in (x,y) = (-4,0)
\[\Large r = \sqrt{x^2+y^2}\]
\[\Large r = \sqrt{(-4)^2+(0)^2}\]
\[\Large r = ???\]

Answer 9

yes r = 4

Answer 10

what nezt

Answer 11

Now let's find theta
\[\Large \theta = \arctan\left(\frac{y}{x}\right)\]
\[\Large \theta = \arctan\left(\frac{0}{-4}\right)\]
\[\Large \theta = ???\]

Answer 12

0 rad

Answer 13

theta = 0 radians or theta = pi radians

(-4,0) corresponds to when theta = pi radians

Answer 14

pi radians = 180 degrees

Answer 15

r = 4
theta = 180 degrees

You'll plug those values into
\[\Large z = r*\left[\cos(\theta)+i*\sin(\theta)\right]\]

Answer 16

ah so i would get this 4(cos 180° + i sin 180°)

Answer 17

yes

Answer 18

Express the complex number in trigonometric form.

-2i

Answer 19

how about that one? thanks btw