Berikut ini adalah kumpulan soal mengenai Limit Trigonometri tipe standar. Jika ada jawaban yang salah, mohon dikoreksi melalui komentar. Terima kasih.
No. 11
\displaystyle\lim_{x\to0}\dfrac{x}{2\csc x\left(1-\sqrt{\cos x}\right)}=
Alternatif Penyelesaian \(\begin{aligned}
\displaystyle\lim_{x\to0}\dfrac{x}{2\csc x\left(1-\sqrt{\cos x}\right)}&=\displaystyle\lim_{x\to0}\dfrac{x}{2\dfrac1{\sin x}\left(1-\sqrt{\cos x}\right)}\color{red}{\cdot\dfrac{1+\sqrt{\cos x}}{1+\sqrt{\cos x}}}\\
&=\displaystyle\lim_{x\to0}\dfrac{x\sin x\left(1+\sqrt{\cos x}\right)}{2\left(1-\cos x\right)}\color{red}{\cdot\dfrac{1+\cos x}{1+\cos x}}\\
&=\displaystyle\lim_{x\to0}\dfrac{x\sin x\left(1+\sqrt{\cos x}\right)(1+\cos x)}{2\left(1-\cos^2x\right)}\\
&=\displaystyle\lim_{x\to0}\dfrac{x\sin x\left(1+\sqrt{\cos x}\right)(1+\cos x)}{2\sin^2x}\\
&=\displaystyle\lim_{x\to0}\dfrac{x\left(1+\sqrt{\cos x}\right)(1+\cos x)}{2\sin x}\\
&=\displaystyle\lim_{x\to0}\dfrac{x}{\sin x}\cdot\displaystyle\lim_{x\to0}\dfrac{\left(1+\sqrt{\cos x}\right)(1+\cos x)}2\\
&=1\cdot\dfrac{\left(1+\sqrt{\cos 0}\right)(1+\cos 0)}2\\
&=\dfrac{\left(1+\sqrt1\right)(1+1)}2\\
&=\dfrac{\left(1+1\right)(\cancel{2})}{\cancel{2}}\\
&=\boxed{\boxed{2}}
\end{aligned}\)
No. 12
Nilai
\displaystyle\lim_{x\to2}\dfrac{\left(x^2-5x+6\right)\sin(x-2)}{\left(x^2-x-2\right)^2} adalah
Alternatif Penyelesaian \(\begin{aligned}
\displaystyle\lim_{x\to2}\dfrac{\left(x^2-5x+6\right)\sin(x-2)}{\left(x^2-x-2\right)^2}&=\displaystyle\lim_{x\to2}\dfrac{(x-3)(x-2)\sin(x-2)}{\left((x+1)(x-2)\right)^2}\\[8pt]
&=\displaystyle\lim_{x\to2}\dfrac{(x-3)(x-2)\sin(x-2)}{(x+1)^2(x-2)^2}\\[8pt]
&=\displaystyle\lim_{x\to2}\dfrac{(x-3)\sin(x-2)}{(x+1)^2(x-2)}\\[8pt]
&=\displaystyle\lim_{x\to2}\dfrac{x-3}{(x+1)^2}\cdot\dfrac{\sin(x-2)}{x-2}\\[8pt]
&=\dfrac{2-3}{(2+1)^2}\cdot1\\[8pt]
&=\dfrac{-1}{(3)^2}\\
&=\boxed{\boxed{-\dfrac19}}
\end{aligned}\)
No. 13
Nilai dari
{\displaystyle\lim_{x\to0}\dfrac{\sin3x+\sin5x}{2x\cos4x}=}
Alternatif Penyelesaian \(\begin{aligned}
\displaystyle\lim_{x\to0}\dfrac{\sin3x+\sin5x}{2x\cos4x}&=\displaystyle\lim_{x\to0}\dfrac{\dfrac{\sin3x}x+\dfrac{\sin5x}x}{\dfrac{2x\cos4x}x}\\
&=\displaystyle\lim_{x\to0}\dfrac{\dfrac{\sin3x}x+\dfrac{\sin5x}x}{2\cos4x}\\
&=\dfrac{3+5}{2\cos4(0)}\\
&=\dfrac8{2(1)}\\
&=\boxed{\boxed{4}}
\end{aligned}\)
No. 14
Nilai
{\displaystyle\lim_{x\to0}\dfrac{x\tan3x}{\sin^2x-\cos2x+1}=}
Alternatif Penyelesaian \(\begin{aligned}
\displaystyle\lim_{x\to0}\dfrac{x\tan3x}{\sin^2x-\cos2x+1}&=\displaystyle\lim_{x\to0}\dfrac{x\tan3x}{\sin^2x-\left(1-2\sin^2x\right)+1}\\[8pt]
&=\displaystyle\lim_{x\to0}\dfrac{x\tan3x}{\sin^2x-1+2\sin^2x+1}\\[8pt]
&=\displaystyle\lim_{x\to0}\dfrac{x\tan3x}{3\sin^2x}\\[8pt]
&=\displaystyle\lim_{x\to0}\dfrac13\cdot\dfrac{x}{\sin x}\cdot\dfrac{\tan3x}{\sin x}\\[8pt]
&=\dfrac13\cdot1\cdot3\\
&=\boxed{\boxed{1}}
\end{aligned}\)
No. 15
\displaystyle\lim_{x\to0}\dfrac{\sin3x}{5x}
Alternatif Penyelesaian
\displaystyle\lim_{x\to0}\dfrac{\sin3x}{5x}=\boxed{\boxed{\dfrac35}}
No. 16
\displaystyle\lim_{x\to0}\dfrac{4\tan5x}{3x}
Alternatif Penyelesaian
\displaystyle\lim_{x\to0}\dfrac{4\tan5x}{3x}=\dfrac{4\cdot5}3=\boxed{\boxed{\dfrac{20}3}}
No. 17
Tentukan nilai dari
\displaystyle\lim_{x\to0}\dfrac{2-2\cos2x}{x^2}
Alternatif Penyelesaian
\(\eqalign{
\displaystyle\lim_{x\to0}\dfrac{2-2\cos2x}{x^2}&=\displaystyle\lim_{x\to0}\dfrac{2-2\left(1-2\sin^2x\right)}{x^2}\\
&=\displaystyle\lim_{x\to0}\dfrac{2-2+4\sin^2x}{x^2}\\
&=\displaystyle\lim_{x\to0}\dfrac{4\sin^2x}{x^2}\\
&=\displaystyle\lim_{x\to0}4\cdot\dfrac{\sin x}x\cdot\dfrac{\sin x}x\\
&=4\cdot1\cdot1\\
&=\boxed{\boxed{4}}
}\)
No. 18
Nilai dari
\displaystyle\lim_{x\to4}\dfrac{x^2-16}{\sin(2x-8)}
Alternatif Penyelesaian
\(\eqalign{
\displaystyle\lim_{x\to4}\dfrac{x^2-16}{\sin(2x-8)}&=\displaystyle\lim_{x\to4}\dfrac{(x+4)(x-4)}{\sin2(x-4)}\\
&=\displaystyle\lim_{x\to4}(x+4)\cdot\displaystyle\lim_{x\to4}\dfrac{x-4}{\sin2(x-4)}
}\)
Misal t=x-4
Jika x\to4 maka t=x-4\to4-4=0
\(\eqalign{
\displaystyle\lim_{x\to4}(x+4)\cdot\displaystyle\lim_{x\to4}\dfrac{x-4}{\sin2(x-4)}&=(4+4)\cdot\displaystyle\lim_{t\to0}\dfrac{t}{\sin2t}\\
&=(8)\cdot\dfrac12\\
&=\boxed{\boxed{4}}
}\)
No. 19
\displaystyle\lim_{x\to0}\dfrac{1-\cos4x}{x\sin x}=
Alternatif Penyelesaian
\(\eqalign{
\displaystyle\lim_{x\to0}\dfrac{1-\cos4x}{x\sin x}&=\displaystyle\lim_{x\to0}\dfrac{1-\left(1-2\sin^22x\right)}{x\sin x}\\
&=\displaystyle\lim_{x\to0}\dfrac{1-1+2\sin^22x}{x\sin x}\\
&=\displaystyle\lim_{x\to0}\dfrac{2\sin^22x}{x\sin x}\\
&=\displaystyle\lim_{x\to0}\left(2\cdot\dfrac{\sin2x}x\cdot\dfrac{\sin2x}{\sin x}\right)\\
&=2\cdot2\cdot2\\
&=\boxed{\boxed{8}}
}\)
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