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> Resenja iz geometrije za zajednicki

Puzzler
post Feb 10 2008, 09:06 PM
Post #21





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Papir "11"

5.

sin^3x-cos^3x=-1
(sinx-cosx)(sin^2x+sinxcosx+cos^2x)=-1
smena: \ \ sinx-cosx=t
(sinx - cosx)^2=1-2sinxcox {\Rightarrow} sinxcosx={\frac{1-t^2}{2}}
(sinx-cosx)(1+sinxcosx)=-1
t(1+{\frac{1-t^2}{2}})=-1
t^3-3t-2=0
(t+1)^2(t-2)=0
t=-1 (*) {\vee} t=2 (**)
[sin2x {\in} [-1,1] {\Rightarrow} sinxcosx {\in} [-{\frac{1}{2}},{\frac{1}{2}}]]

(*) sinx -cosx=-1 {\wedge} sinxcosx=0 {\Rightarrow} (sinx=0 {\wedge} cosx=1) {\vee} (cosx=0 {\wedge} sinx=-1)

...

(**) sinx - cosx=2 {\wedge} sinxcosx={\frac{3}{2}} {\notin} [-{\frac{1}{2}},{\frac{1}{2}}] {\Rightarrow} nema \ resenja








sin3x=sin^3x
3sinx-4sin^3x=sin^3x
5sin^3x-3sinx=0
sinx(5sin^2x-3)=0
sinx=0 {\vee} sin^2x={\frac{3}{5}}

...







sin^6x-cos^6x=sin^3x+cos^3x
(sin^3x-cos^3x)(sin^3x+cos^3x)=sin^3x+cos^3x
(sin^3x-cos^3x-1)(sin^3x+cos^3x)=0
sin^3x-cos^3x=1 {\vee} sin^3x+cos^3x=0
sin^3x-cos^3x=1 {\vee} (sinx+cosx)(sin^2x-sinxcosx+cos^2x)=0
sin^3x-cos^3x=1 {\vee} sinx+cosx=0 {\vee} sinxcosx=1
sin^3x-cos^3x=1 {\vee} sqrt{2}sin(x+{\frac{\pi}{4}}) {\vee} sin2x={\frac{1}{2}}

Druge dve su trivijalne, a prva se rešava istom smenom kao i pod a).




tgx+cos2x=1
tgx+{\frac{1-tg^2x}{1+tg^2x}}=1
tgx+tg^3x+1-tg^2x=1+tg^2x
tg^3x-2tg^2x+tgx=0
tgx(tgx-1)^2=0
tgx=0 {\vee} tgx=1
x=k{\pi} {\vee} x={\frac{\pi}{4}}+k{\pi}, k {\in} Z




2tgx+{\frac{2tgx}{1+tg^2x}}=3
2tgx+2tg^3x+2tgx=3+3tg^2x
2tg^3x-3tg^2x+4tgx-3=0
(tgx-1)(2tg^2x-tgx+3)=0
tgx=1, jer \ je \ 2tg^2x-tgx+3=2(tgx-{\frac{1}{4}})^2+{\frac{7}{8}}>0
x={\frac{\pi}{4}}+k{\pi}, \ k {\in} Z


Ma opusti se Čedo... Malo samopouzdanja puno znači. wink.gif

This post has been edited by Puzzler: Feb 10 2008, 09:07 PM


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Puzzler
post Feb 10 2008, 09:21 PM
Post #22





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Papir "11"

8.

tg(arcsin{\frac{1}{3}}+arctg{\frac{1}{3}}+arccos{\frac{1}{3}})=tg({\frac{\pi}{2}}+arctg{\frac{1}{3}})=-ctg(arctg{\frac{1}{3}})=-ctg(arcctg3)=-3

9.

sin(2arcsin{\frac{3}{5}}+2arccos(-{\frac{4}{5}}))=sin(2arcsin{\frac{3}{5}}+2{\pi}-arccos{\frac{4}{5}})=sin(2arcsin{\frac{3}{5}}-arcsin sqrt{1-({\frac{4}{5}}})^2)=
=sin(2arcsin{\frac{3}{5}}-2arcsin{\frac{3}{5}})=sin0=0

10.

arcsin(sin6)+arccos(sin(6{\pi}-6))=arcsin(sin(6-2{\pi}))+arccos(sin(-6))=arcsin(sin(6-2{\pi}))+arccos(cos{\frac{\pi}{2}}+6))=
=arcsin(sin(6-2{\pi}))+arccos(cos(6-{\frac{3{\pi}}{2}}))=6-2{\pi}+6-{\frac{3{\pi}}{2}}=
[ovo \ vazi \ jer \ 6-2{\pi} {\in} [-{\frac{\pi}{2}},{\frac{\pi}{2}}] \ i \ 6-{\frac{3{\pi}}{2}} {\in} [0,{\pi}]]
=12 - {\frac{7{\pi}}{2}}


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T-Rex
post Feb 10 2008, 09:21 PM
Post #23





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A jos vise znaci kad uzmes malo da ucis biggrin.gif
Al me nesto nece...
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Puzzler
post Feb 10 2008, 09:30 PM
Post #24





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Papir "11"

11.

2-2cosx-4sinx {\le} 0
3-2(1-2sin^2x)-4sinx {\le} 0
3-2+4sin^2x-4sinx{\le}0
4sin^2x-4sinx+1{\le}0
(2sinx-1)^2{\le}0
2sinx-1=0
sinx={\frac{1}{2}}
...



cos2x+cos4x{\ge}0
2cos3xcox{\ge}0
sada nacrtati grafike funkcija cos3x i cosx na intervalu [0,2{\pi}], naći gde su istog znaka, i rešenje su ti intervali + 2k{\pi}.


T-T-T-That all, Folks!!! Nadam se da ćete, kao i ja, sada malo da gledate "Ovo nije glupi tinejdžerski film". Pozz


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^_NiN0_^
post Feb 10 2008, 09:46 PM
Post #25


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Ne kontam koliko ste vi to zadataka imali ?
E gledam ovo nije glup ... aaaaaaaa


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Velika matura deca Yo!hambina)
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NeverMore21
post Feb 10 2008, 10:29 PM
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Nenade spasao si me!!!! Mada cu opet da zabodem 4 u najboljem slucaju, al nema veze!!! Sutra od Baltik tima imas ruchak cheers.gif ...


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NeverMore21
post Feb 10 2008, 10:43 PM
Post #27





Group: Članovi
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QUOTE(T-Rex @ Feb 10 2008, 10:05 PM)
Kako sam glup brate meni ova reshenja nishta ne znache...
Ja sam sutra ugasio, bice iz keca u kec... biggrin.gif
*



Ma neces bre smile.gif , znas ono:

"Kladicu se ovog puta
iz keca u dva
da ce prva da povede
a da slavim ja"

Evo ja se kladim da neces zabosti keca...primas li opkladu? Nemoj samo da namerno nista ne uradis tongue.gif!

This post has been edited by NeverMore21: Feb 10 2008, 11:35 PM


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T-Rex
post Feb 11 2008, 12:49 AM
Post #28





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Opklada prihvacena smile.gif
U pivo cheers.gif
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NeverMore21
post Feb 11 2008, 01:01 AM
Post #29





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Ti castis laugh.gif ...


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T-Rex
post Feb 11 2008, 01:09 AM
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Ja bi voleo smile.gif
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Anchi
post Feb 11 2008, 06:31 PM
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Jao Nenade spasao si nas sa onim resenjima smile.gif biggrin.gif Inace je bilo mnogo lakse nego sto sam mislila da ce biti... Ljubinkina poslednja dva kontrolna su bila 100 puta teza XD.gif
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Hannibal Lecter
post Feb 11 2008, 06:32 PM
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ja sam uradio sve soproud.gif


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How everything still turns to gold
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To be a rock and not to roll


Svi me žele, a ja sam nedodirljiv!
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NeverMore21
post Feb 11 2008, 07:07 PM
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Nisi jedini cool.gif ...


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Hannibal Lecter
post Feb 11 2008, 09:10 PM
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Pa kad je bilo prosto


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And as we wind on down the road
Our shadows taller than our soul
There walks a lady we all know
Who shines white light and wants to show
How everything still turns to gold
And if you listen very hard
The truth will come to you at last
When all are one and one is all
To be a rock and not to roll


Svi me žele, a ja sam nedodirljiv!
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