192.

Trigonometrijski limes

TEKST ZADATKA

Odrediti graničnu vrednost:

limxπsinx1x2π2\lim_{{x} \to {\pi}} \frac {\sin{x}} {1-\frac {x^2} {\pi^2}}

REŠENJE ZADATKA

Srediti imenilac:

limxπsinxπ2x2π2\lim_{{x} \to {\pi}} \frac {\sin{x}} {\frac {\pi^2-x^2} {\pi^2}}

Osloboditi se dvojnog razlomka:

limxππ2sinxπ2x2\lim_{{x} \to {\pi}} \frac {\pi^2*\sin{x}} {\pi^2-x^2}

Primeniti formulu za razliku kvadrata:

limxππ2sinx(πx)(π+x)\lim_{{x} \to {\pi}} \frac {\pi^2*\sin{x}} {(\pi-x)(\pi+x)}

Izvući konstante ispred limesa:

π2limxπsinx(πx)(π+x)\pi^2*\lim_{{x} \to {\pi}} \frac {\sin{x}} {(\pi-x)(\pi+x)}

Uvesti smenu:

πx=u    x=πx\pi-x=u \implies x=\pi-x
DODATNO OBJAŠNJENJE

Uvrstiti smenu u izraz:

π2limu0sin(πu)u(π+πu)=π2limu0sin(πu)u(2πu)\pi^2*\lim_{{u} \to {0}} \frac {\sin{(\pi-u)}} {u(\pi+\pi-u)}= \pi^2*\lim_{{u} \to {0}} \frac {\sin{(\pi-u)}} {u(2\pi-u)}

Primeniti adicionu formulu za sinus razlike: sin(αβ)=sinαcosβsinβcosα\sin{(\alpha-\beta)}=\sin{\alpha}\cos{\beta}-\sin{\beta}\cos{\alpha}

π2limu0sinπcosusinucosπu(2πu) \pi^2*\lim_{{u} \to {0}} \frac {\sin{\pi}\cos{u}-\sin{u}\cos{\pi}} {u(2\pi-u)}

Uvrstiti vrednosti trigonometrijskih funkcija:

π2limu00cosusinu(1)u(2πu)=π2limu0sinuu(2πu) \pi^2*\lim_{{u} \to {0}} \frac {0*\cos{u}-\sin{u}*(-1)} {u(2\pi-u)}= \pi^2*\lim_{{u} \to {0}} \frac {\sin{u}} {u(2\pi-u)}
DODATNO OBJAŠNJENJE

Primeniti tablični limes: limx0sinxx=1 \lim_{{x} \to {0}}\frac {\sin{x}} {x}=1

π212πu\pi^2* \frac 1 {2\pi-u}
DODATNO OBJAŠNJENJE

Zameniti u=0.u=0.

π212π0=π212π=π2\pi^2* \frac 1 {2\pi-0}=\pi^2* \frac 1 {2\pi}=\frac {\pi} 2

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