HIPERBOLA (IRISAN KERUCUT)

 A. Definisi

Hiperbola adalah tempat kedudukan (lokus) titik-titik pada bidang yang memiliki selisih mutlak jarak terhadap dua titik tetap yang disebut fokus bernilai konstan

B. Persamaan hiperbola pusat O(0,0)

Perhatikan ilustrasi berikut

$\begin{aligned}&\text{Keterangan}\\ &\bullet \quad \textrm{F}_{1}\quad \textrm{dan}\quad \textrm{F}_{2}\quad \textrm{disebut fokus}\\ &\bullet \quad \textrm{A dan B disebut puncak}\\  &\bullet \quad \textrm{O disebut puncak}\\ &\bullet \quad \textrm{sumbu X sebagai sumbu utama/nyata/transversal}\\ &\qquad (\textrm{sumbu yang}\quad \textrm{F}_{1}\quad \textrm{dan}\quad \textrm{F}_{2}\quad \textrm{terletak})\\ &\bullet \quad \textrm{sumbu Y sebagai sumbu sekawan/imajiner}\\ &\bullet \quad \textrm{sumbu mayor}=AB=2a\\ &\bullet \quad \textrm{sumbu minor}=RQ=2b\\ &\bullet \quad \textrm{garis}\quad g_{1}\quad \textrm{dan}\quad g_{2}\quad \textrm{disebut garis direktris}\\ &\bullet \quad \textrm{KL dan TS disebut latus rektum, panjangnya}=\displaystyle \frac{2b^{\displaystyle 2}}{a}\\ &\bullet \quad \textrm{garis}\quad y=\pm \displaystyle \frac{b}{a}x\quad \textrm{disebut asimtot miring}\\ &\bullet \quad \textrm{di antara}:a,b,\: \textrm{dan}\: c\quad \textrm{terdapat hubungan}\quad c^{\displaystyle 2}=a^{\displaystyle 2}+b^{\displaystyle 2}\\\end{aligned}$.

$\begin{array}{|l|c|c|}\hline \begin{aligned}&\textrm{Hiperbola}\end{aligned}&\displaystyle \frac{x^{\displaystyle 2}}{a^{\displaystyle 2}}-\displaystyle \frac{y^{\displaystyle 2}}{b^{\displaystyle 2}}=1&\displaystyle \frac{y^{\displaystyle 2}}{a^{\displaystyle 2}}-\displaystyle \frac{x^{\displaystyle 2}}{b^{\displaystyle 2}}=1\\\hline  \textrm{Terbuka}&\textrm{kanan-kiri}&\textrm{atas-bawah}\\\hline \textrm{Fokus}&(\pm c,0)&(0,\pm c)\\\hline \textrm{Puncak}&(\pm a,0)&(0,\pm a)\\\hline \textrm{Asimtot}&y=\pm \displaystyle \frac{b}{a}x&y=\pm \displaystyle \frac{a}{b}x\\\hline \textrm{Direktris}&x=\pm \displaystyle \frac{a^{\displaystyle 2}}{c}&y=\pm \displaystyle \frac{a^{\displaystyle 2}}{c}\\\hline\begin{aligned}&\text{Sumbu}\\ &\textrm{simetri} \end{aligned}&y=0,x=0&y=0,x=0\\\hline \begin{aligned}&\text{Latus}\\ &\textrm{rektum} \end{aligned}&\displaystyle \frac{2b^{\displaystyle 2}}{a}&\displaystyle \frac{2b^{\displaystyle 2}}{a}\\\hline  \textrm{eksentrisitas}&\displaystyle \frac{c}{a}&\displaystyle \frac{c}{a}\\\hline\end{array}$.

C. Persamaan hiperbola pusat (h,k)

Perhatikan tabel berikut

$\begin{array}{|l|c|c|}\hline \begin{aligned}&\textrm{Hiperbola}\end{aligned}&\displaystyle \frac{(x-h)^{\displaystyle 2}}{a^{\displaystyle 2}}-\displaystyle \frac{(y-k)^{\displaystyle 2}}{b^{\displaystyle 2}}=1&\displaystyle \frac{(y-k)^{\displaystyle 2}}{a^{\displaystyle 2}}-\displaystyle \frac{(x-h)^{\displaystyle 2}}{b^{\displaystyle 2}}=1\\\hline  \textrm{Terbuka}&\textrm{kanan-kiri}&\textrm{atas-bawah}\\\hline \textrm{Fokus}&(h\pm c,k)&(h,k\pm c)\\\hline \textrm{Puncak}&(h\pm a,k)&(h,k\pm a)\\\hline \textrm{Asimtot}&y-k=\pm \displaystyle \frac{b}{a}(x-h)&y-k=\pm \displaystyle \frac{a}{b}(x-h)\\\hline \textrm{Direktris}&x=h\pm \displaystyle \frac{a^{\displaystyle 2}}{c}&y=k\pm \displaystyle \frac{a^{\displaystyle 2}}{c}\\\hline\begin{aligned}&\text{Sumbu}\\ &\textrm{simetri} \end{aligned}&y=k,x=h&y=k,x=h\\\hline \begin{aligned}&\text{Latus}\\ &\textrm{rektum} \end{aligned}&\displaystyle \frac{2b^{\displaystyle 2}}{a}&\displaystyle \frac{2b^{\displaystyle 2}}{a}\\\hline  \textrm{eksentrisitas}&\displaystyle \frac{c}{a}&\displaystyle \frac{c}{a}\\\hline\end{array}$.

$\LARGE{CONTOH SOAL}$.

$\begin{array}{ll}\\ 1.&\textrm{Tentukan koordinat pusat, puncak, fokus, asimtot}\\ &\textrm{eksentrisitas, direktris, sb.utama, sb. sekawan,}\\ &\textrm{sb. mayor, sb. minor, dan panjang latus rektum }\\ &\textrm{dari hiperbola}\quad 9x^{\displaystyle 2}-16y^{\displaystyle 2}=144\\\\ &\textrm{Solusi}:\\ &\textrm{Perhatikan bahwa}\quad 9x^{\displaystyle 2}-16y^{\displaystyle 2}=144\\ &\displaystyle \frac{x^{\displaystyle 2}}{16}-\frac{y^{\displaystyle 2}}{9}=1\\ &\begin{aligned}&\bullet \quad a^{\displaystyle 2}=16\Longrightarrow a=4\\ &\bullet \quad b^{\displaystyle 2}=9\Longrightarrow b=3\\ &\bullet \quad c^{\displaystyle 2}=a^{\displaystyle 2}+b^{\displaystyle 2}=16+9=25\Longrightarrow c=5\\ &\textrm{Sehingga diperoleh}\\ &\ast  \quad \textrm{koordinat pusat}:(0,0)\\ &\ast  \quad \textrm{koordinat puncak}:(\pm a,0)=(\pm 4,0)\\ &\ast  \quad \textrm{koordinat fokus}:(\pm c,0)=(\pm 5,0)\\ &\ast  \quad \textrm{asimtot}:y=\pm \displaystyle \frac{b}{a}x\Rightarrow y=\pm \displaystyle \frac{3}{4}x\\ &\ast  \quad \textrm{eksentrisitas}\quad e=\displaystyle \frac{c}{a}=\displaystyle \frac{5}{4}\\ &\ast  \quad \textrm{direktris}:x=\displaystyle \pm \frac{a^{\displaystyle 2}}{c}=\pm \frac{16}{5}\\ &\ast  \quad \textrm{sumbu utama}:y=0\\ &\ast  \quad \textrm{sumbu sekawan}:x=0\\ &\ast  \quad \textrm{sumbu mayor}:2a=2.4=8\\ &\ast  \quad \textrm{sumbu minor}:2b=2.3=6\\ &\ast  \quad \textrm{latus rektum}:\displaystyle \frac{2b^{\displaystyle 2}}{a}=\displaystyle \frac{18}{4}=\frac{9}{2}\\\end{aligned} \end{array}$.