Latihan Matematika Peminatan Kelas XII Limit Fungsi Trigonometri
# 7
Pilgan

Nilai dari limx1 (x21)tan(6x6)sin2(x1)=....\lim\limits_{x\rightarrow1}\ \frac{\left(x^2-1\right)\tan\left(6x-6\right)}{\sin^2\left(x-1\right)}=....

A

44

B

33

C

66

D

1010

E

1212

Pembahasan:

Subtitusi x=1x=1 menghasilkan nilai tak tentu 00\frac{0}{0}

Ingat bahwa

limx0 axsinbx=ab\lim\limits_{x\rightarrow0}\ \frac{ax}{\sin bx}=\frac{a}{b}

limx0 tanaxsinbx=ab\lim\limits_{x\rightarrow0}\ \frac{\tan ax}{\sin bx}=\frac{a}{b}

Bentuk (x21)\left(x^2-1\right) dapat difaktorkan menjadi x21=(x1)(x+1)x^2-1=\left(x-1\right)\left(x+1\right) , maka

limx1 (x21)tan(6x6)sin2(x1)=limx1 (x1)(x+1)tan6(x1)sin2(x1)\lim\limits_{x\rightarrow1}\ \frac{\left(x^2-1\right)\tan\left(6x-6\right)}{\sin^2\left(x-1\right)}=\lim\limits_{x\rightarrow1}\ \frac{\left(x-1\right)\left(x+1\right)\tan6\left(x-1\right)}{\sin^2\left(x-1\right)}

=limx1 ((x1)sin(x1)(x+1)tan6(x1)sin(x1))=\lim\limits_{x\rightarrow1}\ \left(\frac{\left(x-1\right)}{\sin\left(x-1\right)}\cdot\left(x+1\right)\cdot\frac{\tan6\left(x-1\right)}{\sin\left(x-1\right)}\right)

=limx1 (x1)sin(x1)limx1 (x+1)limx1 tan6(x1)sin(x1)=\lim\limits_{x\rightarrow1}\ \frac{\left(x-1\right)}{\sin\left(x-1\right)}\cdot\lim\limits_{x\rightarrow1}\ \left(x+1\right)\cdot\lim\limits_{x\rightarrow1}\ \frac{\tan6\left(x-1\right)}{\sin\left(x-1\right)}

=1limx1 (x+1)6=1\cdot\lim\limits_{x\rightarrow1}\ \left(x+1\right)\cdot6

=1(1+1)6=1\cdot\left(1+1\right)\cdot6

=12=12

Jadi, nilai dari limx1 (x21)tan(6x6)sin2(x1)=12\lim\limits_{x\rightarrow1}\ \frac{\left(x^2-1\right)\tan\left(6x-6\right)}{\sin^2\left(x-1\right)}=12