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MaxWong

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MaxWong  13 janv. 2019
 #2
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I think of eiθ=cosθ+isinθ......

 

Let me try :) (Im just a kid don't blame me if I did anything wrong....... Just point out the mistake......)

 

4sinx=ex4sinx=e(i4x)i4=14sinx=ei(xi3)4sinx=ei(ix)i3=i4sinx=cos(ix)+isin(ix)

 

We are going to introduce 4 formulae here:

 

1) sin(x)=sinx

 

2)cos(x)=cosx

 

3)cos(ix)=coshx=ex+ex2

 

4)sin(ix)=isinhx=exex2i

 

Now continue.....

Last step done was:

 4sinx=cos(ix)+isin(ix)4sinx=cos(ix)isin(ix)Formulae 1 and 24sinx=ex+ex2+exex2=exFormulae 3 and 4

 

Nope it just goes back to 4 sin x = e^x....... Sob sob :(

 

Another method!!

 

4sinx=ex

 

We are going to introduce the definition of sin x this time....... (If it doesn't work Im going to use Taylor series :( )

 

4(eixeix2i)=ex2eix2eixi=ex2ieix2ieix=ex1i=i2i(1eixeix)=ex2i(1e2ixeix)=ex

 

Np.

 

I never give up!!!

 

Another method!!

 

4(xx33!x55!+x77!+x99!)=ex

 

Still np......

 

Sigh maybe I am just too dull and can't see the method...... 

 

PS I am 14 :)

27 janv. 2017
 #8
avatar+9675 
+5
26 janv. 2017