Trigo Flashcards

1
Q

cos(x)^2+ sin(x)^2=

A

1

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2
Q

1+tan(x)^2=

A

1/cos(x)^2

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3
Q

1+cotan(x)^2=

A

1/sin(x)^2

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4
Q

cos(x)=

en sin

A

sin(x+π/2) ou sin(π/2-x)

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5
Q

sin(x) =

en cos

A

cos(π/2-x) ou cos(x-π/2)

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6
Q
  • cos(x)=
A

cos(x+π) ou cos(π-x)

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7
Q
  • sin(x)=
A

sin(-x) ou sin(x+π)

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8
Q

cos(x)=

Formule d’Euler

A

(e^ix+e^-ix)/2

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9
Q

e^ix+e^-ix=

A

2cos(x)

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10
Q

sin(x)=

Formule d’Euler

A

(e^ix-e^-ix)/2i

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11
Q

e^ix-e^-ix=

A

2isin(x)

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12
Q

Formule d’Euler démonstration sinus

A

système avec e^ix e^-ix

on soustrait

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13
Q

Formule d’Euler démonstration cosinus

A

système avec e^ix e^-ix

on additionne

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14
Q

Formule de Moivre:

(cos(ϑ)+isin(ϑ))^n=

A

cos(nϑ)+isin(nϑ)

(car (e^iϑ)^n = e^inϑ

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15
Q

cos(a + b) =

A

cos(a)cos(b) − sin(a)sin(b)

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16
Q

cos(a − b) =

A

cos(a)cos(b) + sin(a)sin(b)

17
Q

sin(a − b) =

A

sin(a)cos(b) − sin(b)cos(a)

18
Q

sin(a + b) =

A

sin(a)cos(b) + sin(b)cos(a)

19
Q

cos(2a) =

A

cos(a)^2 − sin(a)^2
= 2cos(a)^2 − 1
= 1 − 2sin(a)^2

20
Q

sin(2a) =

A

2sin(a)cos(a)

21
Q

2cos(x)=

A

e^ix+e^-ix

22
Q

2isin(x)

A

e^ix-e^-ix

23
Q

Transformer des produits et des puissances de sinus et cosinus en somme de sinus et cosinus:

A

1) Remplacer sin et cos par les formules d’Euler
2) Développer et simplifier
3) Rassembler les e^ix et e^-ix
4) Utiliser ls formules d’Euler “à l’envers”

24
Q

cos(nϑ)+isin(nϑ)=

A

Formule de Moivre:

(cos(ϑ)+isin(ϑ))^n

25
Q

Pour trouver une formule trigonométrique de cos(nx) ou sin(nx)

A

1) cos(nx)= Re(e^inx) , sin(nx) = Im(e^inx)
2) e^inx = (e^ix)^n
3) On remplace e^ix par cos(x) + sin(x)
4) On développe…

26
Q

1=

A

e^0 donc cos(0)

27
Q

i=

A

e^π/2 donc sin(π/2)

28
Q

La technique de l’arc moitié consiste à:

A

transformer un nombre complexe de la forme e^ia+e^ib ou e^ia-e^ib
1)On factorise par e^i(a+b)/2
2)On utilise les formules d’Euler pour faire apparaître cos ou sin.
La technique permet d’établir des formules trigonométriques.

29
Q

1/i