Tenemos la indeterminación de tipo
0/0, tal que el límite para el numerador es
lim x → π 2 + 1 tan ( 5 x ) = 0 \lim_{x \to \frac{\pi}{2}^+} \frac{1}{\tan{\left(5 x \right)}} = 0 x → 2 π + lim tan ( 5 x ) 1 = 0 y el límite para el denominador es
lim x → π 2 + 1 log ( 2 x − π 2 ) = 0 \lim_{x \to \frac{\pi}{2}^+} \frac{1}{\log{\left(\frac{2 x - \pi}{2} \right)}} = 0 x → 2 π + lim log ( 2 2 x − π ) 1 = 0 Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
lim x → π 2 + ( log ( x − π 2 ) tan ( 5 x ) ) \lim_{x \to \frac{\pi}{2}^+}\left(\frac{\log{\left(x - \frac{\pi}{2} \right)}}{\tan{\left(5 x \right)}}\right) x → 2 π + lim ( tan ( 5 x ) log ( x − 2 π ) ) =
Introducimos una pequeña modificación de la función bajo el signo del límite
lim x → π 2 + ( log ( 2 x − π 2 ) tan ( 5 x ) ) \lim_{x \to \frac{\pi}{2}^+}\left(\frac{\log{\left(\frac{2 x - \pi}{2} \right)}}{\tan{\left(5 x \right)}}\right) x → 2 π + lim ( tan ( 5 x ) log ( 2 2 x − π ) ) =
lim x → π 2 + ( d d x 1 tan ( 5 x ) d d x 1 log ( 2 x − π 2 ) ) \lim_{x \to \frac{\pi}{2}^+}\left(\frac{\frac{d}{d x} \frac{1}{\tan{\left(5 x \right)}}}{\frac{d}{d x} \frac{1}{\log{\left(\frac{2 x - \pi}{2} \right)}}}\right) x → 2 π + lim d x d l o g ( 2 2 x − π ) 1 d x d t a n ( 5 x ) 1 =
lim x → π 2 + ( − ( 2 x − π ) ( − 5 tan 2 ( 5 x ) − 5 ) log ( x − π 2 ) 2 2 tan 2 ( 5 x ) ) \lim_{x \to \frac{\pi}{2}^+}\left(- \frac{\left(2 x - \pi\right) \left(- 5 \tan^{2}{\left(5 x \right)} - 5\right) \log{\left(x - \frac{\pi}{2} \right)}^{2}}{2 \tan^{2}{\left(5 x \right)}}\right) x → 2 π + lim ( − 2 tan 2 ( 5 x ) ( 2 x − π ) ( − 5 tan 2 ( 5 x ) − 5 ) log ( x − 2 π ) 2 ) =
lim x → π 2 + ( d d x ( − ( 2 x − π ) log ( x − π 2 ) 2 2 tan 2 ( 5 x ) ) d d x 1 − 5 tan 2 ( 5 x ) − 5 ) \lim_{x \to \frac{\pi}{2}^+}\left(\frac{\frac{d}{d x} \left(- \frac{\left(2 x - \pi\right) \log{\left(x - \frac{\pi}{2} \right)}^{2}}{2 \tan^{2}{\left(5 x \right)}}\right)}{\frac{d}{d x} \frac{1}{- 5 \tan^{2}{\left(5 x \right)} - 5}}\right) x → 2 π + lim d x d − 5 t a n 2 ( 5 x ) − 5 1 d x d ( − 2 t a n 2 ( 5 x ) ( 2 x − π ) l o g ( x − 2 π ) 2 ) =
lim x → π 2 + ( 10 x log ( x − π 2 ) 2 tan ( 5 x ) + 10 x log ( x − π 2 ) 2 tan 3 ( 5 x ) − 2 x log ( x − π 2 ) x tan 2 ( 5 x ) − π tan 2 ( 5 x ) 2 − 5 π log ( x − π 2 ) 2 tan ( 5 x ) − log ( x − π 2 ) 2 tan 2 ( 5 x ) − 5 π log ( x − π 2 ) 2 tan 3 ( 5 x ) + π log ( x − π 2 ) x tan 2 ( 5 x ) − π tan 2 ( 5 x ) 2 50 tan 3 ( 5 x ) 25 tan 4 ( 5 x ) + 50 tan 2 ( 5 x ) + 25 + 50 tan ( 5 x ) 25 tan 4 ( 5 x ) + 50 tan 2 ( 5 x ) + 25 ) \lim_{x \to \frac{\pi}{2}^+}\left(\frac{\frac{10 x \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan{\left(5 x \right)}} + \frac{10 x \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan^{3}{\left(5 x \right)}} - \frac{2 x \log{\left(x - \frac{\pi}{2} \right)}}{x \tan^{2}{\left(5 x \right)} - \frac{\pi \tan^{2}{\left(5 x \right)}}{2}} - \frac{5 \pi \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan{\left(5 x \right)}} - \frac{\log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan^{2}{\left(5 x \right)}} - \frac{5 \pi \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan^{3}{\left(5 x \right)}} + \frac{\pi \log{\left(x - \frac{\pi}{2} \right)}}{x \tan^{2}{\left(5 x \right)} - \frac{\pi \tan^{2}{\left(5 x \right)}}{2}}}{\frac{50 \tan^{3}{\left(5 x \right)}}{25 \tan^{4}{\left(5 x \right)} + 50 \tan^{2}{\left(5 x \right)} + 25} + \frac{50 \tan{\left(5 x \right)}}{25 \tan^{4}{\left(5 x \right)} + 50 \tan^{2}{\left(5 x \right)} + 25}}\right) x → 2 π + lim 25 t a n 4 ( 5 x ) + 50 t a n 2 ( 5 x ) + 25 50 t a n 3 ( 5 x ) + 25 t a n 4 ( 5 x ) + 50 t a n 2 ( 5 x ) + 25 50 t a n ( 5 x ) t a n ( 5 x ) 10 x l o g ( x − 2 π ) 2 + t a n 3 ( 5 x ) 10 x l o g ( x − 2 π ) 2 − x t a n 2 ( 5 x ) − 2 π t a n 2 ( 5 x ) 2 x l o g ( x − 2 π ) − t a n ( 5 x ) 5 π l o g ( x − 2 π ) 2 − t a n 2 ( 5 x ) l o g ( x − 2 π ) 2 − t a n 3 ( 5 x ) 5 π l o g ( x − 2 π ) 2 + x t a n 2 ( 5 x ) − 2 π t a n 2 ( 5 x ) π l o g ( x − 2 π ) =
lim x → π 2 + ( 10 x log ( x − π 2 ) 2 tan ( 5 x ) + 10 x log ( x − π 2 ) 2 tan 3 ( 5 x ) − 2 x log ( x − π 2 ) x tan 2 ( 5 x ) − π tan 2 ( 5 x ) 2 − 5 π log ( x − π 2 ) 2 tan ( 5 x ) − log ( x − π 2 ) 2 tan 2 ( 5 x ) − 5 π log ( x − π 2 ) 2 tan 3 ( 5 x ) + π log ( x − π 2 ) x tan 2 ( 5 x ) − π tan 2 ( 5 x ) 2 50 tan 3 ( 5 x ) 25 tan 4 ( 5 x ) + 50 tan 2 ( 5 x ) + 25 + 50 tan ( 5 x ) 25 tan 4 ( 5 x ) + 50 tan 2 ( 5 x ) + 25 ) \lim_{x \to \frac{\pi}{2}^+}\left(\frac{\frac{10 x \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan{\left(5 x \right)}} + \frac{10 x \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan^{3}{\left(5 x \right)}} - \frac{2 x \log{\left(x - \frac{\pi}{2} \right)}}{x \tan^{2}{\left(5 x \right)} - \frac{\pi \tan^{2}{\left(5 x \right)}}{2}} - \frac{5 \pi \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan{\left(5 x \right)}} - \frac{\log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan^{2}{\left(5 x \right)}} - \frac{5 \pi \log{\left(x - \frac{\pi}{2} \right)}^{2}}{\tan^{3}{\left(5 x \right)}} + \frac{\pi \log{\left(x - \frac{\pi}{2} \right)}}{x \tan^{2}{\left(5 x \right)} - \frac{\pi \tan^{2}{\left(5 x \right)}}{2}}}{\frac{50 \tan^{3}{\left(5 x \right)}}{25 \tan^{4}{\left(5 x \right)} + 50 \tan^{2}{\left(5 x \right)} + 25} + \frac{50 \tan{\left(5 x \right)}}{25 \tan^{4}{\left(5 x \right)} + 50 \tan^{2}{\left(5 x \right)} + 25}}\right) x → 2 π + lim 25 t a n 4 ( 5 x ) + 50 t a n 2 ( 5 x ) + 25 50 t a n 3 ( 5 x ) + 25 t a n 4 ( 5 x ) + 50 t a n 2 ( 5 x ) + 25 50 t a n ( 5 x ) t a n ( 5 x ) 10 x l o g ( x − 2 π ) 2 + t a n 3 ( 5 x ) 10 x l o g ( x − 2 π ) 2 − x t a n 2 ( 5 x ) − 2 π t a n 2 ( 5 x ) 2 x l o g ( x − 2 π ) − t a n ( 5 x ) 5 π l o g ( x − 2 π ) 2 − t a n 2 ( 5 x ) l o g ( x − 2 π ) 2 − t a n 3 ( 5 x ) 5 π l o g ( x − 2 π ) 2 + x t a n 2 ( 5 x ) − 2 π t a n 2 ( 5 x ) π l o g ( x − 2 π ) =
0 0 0 Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 2 vez (veces)