e

Imaginary

negative number: change direction on 1D line. (ex: -4 north = go south 4)

imaginary number: rotate on complex plane.

Exponential

step growth = next step, double the current

natural growth = consider each part, grow little by littlehttps://www.youtube.com/watch?v=_-x90wGBD8U&feature=youtu.be

Euler Formula

https://www.youtube.com/watch?v=qpOj98VNJi4

Euler Formula = 2 ways to move on a circle: (1) x, y, (2) radian

exponential growth

  • real exponential growth = increase by 1 after an interval

  • imaginary exponential growth = rotate 1 after an interval

rotate pi will move to -1.

What is exe^x?

ee = Start at 1, growing continuously to 100% interest after 1 unit of time.

exe^x= Start at 1, growing continuously to 100% interest after x unit of time.

343 ^ 4 = growing from 1 to 3, growth rate = 4x

What is eie ^ i?

eie ^ i = Start at 1, rotating 1 after 1 unit of time.

What is 3i3 ^ i?

ei=cos(1)+iâ‹…sin(i)=0.54+0.84ie ^ i = cos(1) + i \cdot sin(i) = 0.54 + 0.84 i

3i=1â‹…3i3 ^ i = 1 \cdot 3 ^ i

3i=(eln(3))i3 ^ i = (e ^{ln(3)}) ^ i

ln(3) 1.1>1=ln(e)=ln(2.718)ln(3) ~ 1.1 > 1 = ln(e) = ln(2.718)

3i=cos(ln(3))+iâ‹…sin(ln(3))=0.45+0.89i3 ^ i = cos(ln(3)) + i \cdot sin(ln(3)) = 0.45 + 0.89i

What is iii ^ i?

ii=1â‹…iii ^ i = 1 \cdot i ^ i

i=cos(Ï€/2)+iâ‹…sin(Ï€/2)=eiâ‹…Ï€/2i = cos(\pi / 2) + i \cdot sin(\pi / 2) = e ^ {i \cdot {\pi / 2}}

ii=ei⋅i⋅π/2=eπ/2∼0.2i ^ i = e ^ {i \cdot i \cdot \pi / 2} = e ^ {\pi / 2} \sim 0.2

it is shrinking.

Scaling & rotation

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