Derivatives of trigonometric functions

  • Thread starter Brunno
  • Start date
  • #1
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Homework Statement


I'm learning now about darivative all by my self (without a teacher) and I'm not sure about this development

Homework Equations







The Attempt at a Solution



[tex]Y=senx[/tex]

[tex]y+{\Delta}Y=sen(x+{\Delta}Y)[/tex]

[tex]{\Delta}Y=senx*cos{\Delta}x+ sen{\Delta}x*cosx[/tex]

What about this cos,what is it doing in the equation?
I really don't get it.
 

Answers and Replies

  • #2
437
1


this comes from the double angle formula.

it says that: sin (A + B) = sinAcosB + sinBcosA

you can find the same thing for sin (x + dY)
 
  • #3
80
0


Oh,now I think i get it!
Thankyou!
 

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