Maths! Where am i going wrong?

FrostedNipple

FrostedNipple

FrostedNipple

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Show that Sin3θ = 3sinθ - 4sin^3θ

Sin3θ = Sin(2θ + θ)

= Sin2θcosθ + cos2θsinθ

=2sinθcosθcosθ + (1 - 2sin^2θ)sinθ

=2sinθcos^2θ + sinθ - 2sin^3θ

Am i going wrong? If I'm not, what next?
 
baby I wish I was cos squared theta, and you were sin squared theta, that way I'd always be tangent to your curves.
 
You got to:
2sinθcos^2θ + sinθ - 2sin^3θ

Then:
2sinθ(1-sin^2θ) + sinθ - 2sin^3θ

(as cos^2θ = 1 - sin^2θ)

= 2sinθ - 2sin^3θ + sinθ -2sin^3θ

= 3sinθ - 4sin^3θ

:) Done.
 
Ben M said:
baby I wish I was cos squared theta, and you were sin squared theta, that way I'd always be tangent to your curves.
Click to expand...

digged hehe

Show that Sin3θ = 3sinθ - 4sin^3θ

Sin3θ = Sin(2θ + θ)

= Sin2θcosθ + cos2θsinθ

=2sinθcosθcosθ + (1 - 2sin^2θ)sinθ

=2sinθcos^2θ + sinθ - 2sin^3θ

Am i going wrong? If I'm not, what next?
Click to expand...

u should be on the dole not doing maths :D
 
Ben M said:
baby I wish I was cos squared theta, and you were sin squared theta, that way I'd always be tangent to your curves.
Click to expand...

Is that correct, I know a hot girl doing physics and it's the end of year party tonight so cheesinesses + alcohol may make this work ¬_¬
 
Tefal said:
Is that correct, I know a hot girl doing physics and it's the end of year party tonight so cheesinesses + alcohol may make this work ¬_¬
Click to expand...

I think so lol.

It's pretty old, go on any "nerdy chatup lines" page and I can almost guarantee that will be there.

You could just tell her the two atoms joke:

two atoms are walking along, one says to the other "I think i've lost an electron"
The other replies "are you sure?"
"yes, i'm positive"

or...


A neutron walks into a bar, and orders a pint. The barman gives him the pint and starts to walk away. The neutron says "How much is it sir?"
The barman replies "for you, no charge"
 
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