Fungsi f dengan wilayah R dikatakan periodik apabila ada bilangan alt="p \ne 0" src="https://s0.wp.com/latex.php?latex=p+%5Cne+0&bg=f9f9f9&fg=000000&s=0" title="p \ne 0" /> , sedemikian sehingga alt="f(x+p) = f(x)" src="https://s0.wp.com/latex.php?latex=f%28x%2Bp%29+%3D+f%28x%29&bg=f9f9f9&fg=000000&s=0" title="f(x+p) = f(x)" /> , dengan alt="x \epsilon R" src="https://s0.wp.com/latex.php?latex=x+%5Cepsilon+R&bg=f9f9f9&fg=000000&s=0" title="x \epsilon R" /> . Bilangan positif p terkecil yang memenuhi alt="f(x+p) = f(x)" src="https://s0.wp.com/latex.php?latex=f%28x%2Bp%29+%3D+f%28x%29&bg=f9f9f9&fg=000000&s=0" title="f(x+p) = f(x)" /> disebut periode dasar fungsi f.
Jika fungsi f periodik dengan periode dasar p, maka periode-periode dari fungsi f adalah
1. Periode fungsi sinus dan kosinus
Untuk penambahan panjang busur
alt="\sin (a+k \times 2\pi) = \sin a" src="https://s0.wp.com/latex.php?latex=%5Csin+%28a%2Bk+%5Ctimes+2%5Cpi%29+%3D+%5Csin+a&bg=f9f9f9&fg=000000&s=0" title="\sin (a+k \times 2\pi) = \sin a" /> dengan k∈B ataualt="\sin (a+k\times 360^{\circ}) = \sin a^{\circ}" src="https://s0.wp.com/latex.php?latex=%5Csin+%28a%2Bk%5Ctimes+360%5E%7B%5Ccirc%7D%29+%3D+%5Csin+a%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="\sin (a+k\times 360^{\circ}) = \sin a^{\circ}" /> dengan k∈Balt="\cos (a+k\times 2\pi)" src="https://s0.wp.com/latex.php?latex=%5Ccos+%28a%2Bk%5Ctimes+2%5Cpi%29&bg=f9f9f9&fg=000000&s=0" title="\cos (a+k\times 2\pi)" /> dengan k∈B ataualt="\cos (a+ k\times 360^{\circ})" src="https://s0.wp.com/latex.php?latex=%5Ccos+%28a%2B+k%5Ctimes+360%5E%7B%5Ccirc%7D%29&bg=f9f9f9&fg=000000&s=0" title="\cos (a+ k\times 360^{\circ})" /> dengan k∈B
Dengan demikian, fungsi sinus
Baca Juga :
Pengertian Trigonometri dan Rumus Trigonometri Lengkap dengan Soal
Perbandingan Trigonometri dan Tabel Trigonometri Lengkap
2. Periode fungsi tangen
Untuk penambahan panjang busur
Dengan demikian tangen
Grafik Fungsi Trigonometri
Dengan td adalah tidak didefinisikan. Untuk memudahkan, maka lihatlah segitiga berikut :
Dari konsep segitiga tersebut diperoleh nilai setiap sudut
Didapat :
alt="\sin a = \frac{y}{r}" src="https://s0.wp.com/latex.php?latex=%5Csin+a+%3D+%5Cfrac%7By%7D%7Br%7D&bg=f9f9f9&fg=000000&s=0" title="\sin a = \frac{y}{r}" /> alt="cos a = \frac{x}{r}" src="https://s0.wp.com/latex.php?latex=cos+a+%3D+%5Cfrac%7Bx%7D%7Br%7D&bg=f9f9f9&fg=000000&s=0" title="cos a = \frac{x}{r}" /> alt="\tan a = \frac{y}{x}" src="https://s0.wp.com/latex.php?latex=%5Ctan+a+%3D+%5Cfrac%7By%7D%7Bx%7D&bg=f9f9f9&fg=000000&s=0" title="\tan a = \frac{y}{x}" />
Jika titik
alt="\sin 0^{\circ} = \frac{0}{r} = 0" src="https://s0.wp.com/latex.php?latex=%5Csin+0%5E%7B%5Ccirc%7D+%3D+%5Cfrac%7B0%7D%7Br%7D+%3D+0&bg=f9f9f9&fg=000000&s=0" title="\sin 0^{\circ} = \frac{0}{r} = 0" /> alt="\cos 0^{\circ} = \frac{r}{r} = 1" src="https://s0.wp.com/latex.php?latex=%5Ccos+0%5E%7B%5Ccirc%7D+%3D+%5Cfrac%7Br%7D%7Br%7D+%3D+1&bg=f9f9f9&fg=000000&s=0" title="\cos 0^{\circ} = \frac{r}{r} = 1" /> alt="\tan 0^{\circ} = \frac{0}{r} = 0" src="https://s0.wp.com/latex.php?latex=%5Ctan+0%5E%7B%5Ccirc%7D+%3D+%5Cfrac%7B0%7D%7Br%7D+%3D+0&bg=f9f9f9&fg=000000&s=0" title="\tan 0^{\circ} = \frac{0}{r} = 0" />
Jika titik P(x,y)
alt="\sin 90^{\circ} = \frac{r}{r} = 1" src="https://s0.wp.com/latex.php?latex=%5Csin+90%5E%7B%5Ccirc%7D+%3D+%5Cfrac%7Br%7D%7Br%7D+%3D+1&bg=f9f9f9&fg=000000&s=0" title="\sin 90^{\circ} = \frac{r}{r} = 1" /> alt="\cos 0^{\circ} = \frac{0}{r} = 0" src="https://s0.wp.com/latex.php?latex=%5Ccos+0%5E%7B%5Ccirc%7D+%3D+%5Cfrac%7B0%7D%7Br%7D+%3D+0&bg=f9f9f9&fg=000000&s=0" title="\cos 0^{\circ} = \frac{0}{r} = 0" /> - tan
alt="\tan 0^{\circ} = \frac{r}{0}" src="https://s0.wp.com/latex.php?latex=%5Ctan+0%5E%7B%5Ccirc%7D+%3D+%5Cfrac%7Br%7D%7B0%7D&bg=f9f9f9&fg=000000&s=0" title="\tan 0^{\circ} = \frac{r}{0}" /> = tidak didefinisikan
Nilai Maksimum dan Minimum Fungsi Trigonometri
Untuk setiap titik P(x,y)
alt="-r \le x \le r" src="https://s0.wp.com/latex.php?latex=-r+%5Cle+x+%5Cle+r&bg=f9f9f9&fg=000000&s=0" title="-r \le x \le r" /> danalt="-r \le y \le r" src="https://s0.wp.com/latex.php?latex=-r+%5Cle+y+%5Cle+r&bg=f9f9f9&fg=000000&s=0" title="-r \le y \le r" /> alt="-1 \le \frac{x}{r} \le 1" src="https://s0.wp.com/latex.php?latex=-1+%5Cle+%5Cfrac%7Bx%7D%7Br%7D+%5Cle+1&bg=f9f9f9&fg=000000&s=0" title="-1 \le \frac{x}{r} \le 1" /> danalt="-1 \le \frac{y}{r} \le 1" src="https://s0.wp.com/latex.php?latex=-1+%5Cle+%5Cfrac%7By%7D%7Br%7D+%5Cle+1&bg=f9f9f9&fg=000000&s=0" title="-1 \le \frac{y}{r} \le 1" /> alt="-1 \le \cos a \le 1" src="https://s0.wp.com/latex.php?latex=-1+%5Cle+%5Ccos+a+%5Cle+1&bg=f9f9f9&fg=000000&s=0" title="-1 \le \cos a \le 1" /> danalt="-1 \le \sin a \le 1" src="https://s0.wp.com/latex.php?latex=-1+%5Cle+%5Csin+a+%5Cle+1&bg=f9f9f9&fg=000000&s=0" title="-1 \le \sin a \le 1" />
Berdasarkan uraian tersebut dapat dikemukakan bahwa :
Nilai maksimum dan minimum fungsi sinus
- Fungsi sinus
alt="y =f(x) = \sin x" src="https://s0.wp.com/latex.php?latex=y+%3Df%28x%29+%3D+%5Csin+x&bg=f9f9f9&fg=000000&s=0" title="y =f(x) = \sin x" /> memiliki nilai maksimumalt="y_{maks} = 1" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+1&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = 1" /> yang dicapai untukalt="x =\frac{1}{2}\pi + k \times 2\pi" src="https://s0.wp.com/latex.php?latex=x+%3D%5Cfrac%7B1%7D%7B2%7D%5Cpi+%2B+k+%5Ctimes+2%5Cpi&bg=f9f9f9&fg=000000&s=0" title="x =\frac{1}{2}\pi + k \times 2\pi" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> dan nilai minimumalt="y_{min} = -1" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D+%3D+-1&bg=f9f9f9&fg=000000&s=0" title="y_{min} = -1" /> yang dicapai untukalt="x = \frac{3}{2}\pi + k \times 2\pi" src="https://s0.wp.com/latex.php?latex=x+%3D+%5Cfrac%7B3%7D%7B2%7D%5Cpi+%2B+k+%5Ctimes+2%5Cpi&bg=f9f9f9&fg=000000&s=0" title="x = \frac{3}{2}\pi + k \times 2\pi" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> . - Fungsi sinus
alt="y = f(x) = \sin x^{\circ}" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29+%3D+%5Csin+x%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="y = f(x) = \sin x^{\circ}" /> memiliki nilai maksimumalt="y_{maks} = 1" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+1&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = 1" /> yang dicapai untukalt="x = 90^{\circ} + k \times 360^{\circ}" src="https://s0.wp.com/latex.php?latex=x+%3D+90%5E%7B%5Ccirc%7D+%2B+k+%5Ctimes+360%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="x = 90^{\circ} + k \times 360^{\circ}" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> dan nilai minimumalt="y_{maks} = -1" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+-1&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = -1" /> yang dicapai untukalt="x = 270^{\circ} + k \times 360^{\circ}" src="https://s0.wp.com/latex.php?latex=x+%3D+270%5E%7B%5Ccirc%7D+%2B+k+%5Ctimes+360%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="x = 270^{\circ} + k \times 360^{\circ}" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> .
Nilai maksimum dan minimum fungsi kosinus
- Fungsi kosinus
alt="y = f(x) = \cos x" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29+%3D+%5Ccos+x&bg=f9f9f9&fg=000000&s=0" title="y = f(x) = \cos x" /> memiliki nilai maksimumalt="y_{maks} = 1" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+1&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = 1" /> yang dicapai untukalt="x =k \times 2\pi" src="https://s0.wp.com/latex.php?latex=x+%3Dk+%5Ctimes+2%5Cpi&bg=f9f9f9&fg=000000&s=0" title="x =k \times 2\pi" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> dan nilai minimumalt="y_{min} = -1" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D+%3D+-1&bg=f9f9f9&fg=000000&s=0" title="y_{min} = -1" /> yang dicapai untukalt="x = \pi + k \times 2\pi" src="https://s0.wp.com/latex.php?latex=x+%3D+%5Cpi+%2B+k+%5Ctimes+2%5Cpi&bg=f9f9f9&fg=000000&s=0" title="x = \pi + k \times 2\pi" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> . - Fungsi kosinus
alt="y = f(x) = \cos x^{\circ}" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29+%3D+%5Ccos+x%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="y = f(x) = \cos x^{\circ}" /> memiliki nilai maksimumalt="y_{maks} = 1" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+1&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = 1" /> yang dicapai untukalt="x = k \times 360^{\circ}" src="https://s0.wp.com/latex.php?latex=x+%3D+k+%5Ctimes+360%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="x = k \times 360^{\circ}" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> dan nilai minimumalt="y_{min} = -1" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D+%3D+-1&bg=f9f9f9&fg=000000&s=0" title="y_{min} = -1" /> yang dicapai untukalt="x = 180^{\circ} + k \times 360^{\circ}" src="https://s0.wp.com/latex.php?latex=x+%3D+180%5E%7B%5Ccirc%7D+%2B+k+%5Ctimes+360%5E%7B%5Ccirc%7D&bg=f9f9f9&fg=000000&s=0" title="x = 180^{\circ} + k \times 360^{\circ}" /> denganalt="k \epsilon B" src="https://s0.wp.com/latex.php?latex=k+%5Cepsilon+B&bg=f9f9f9&fg=000000&s=0" title="k \epsilon B" /> .
Secara umum dapat dikemukakan bahwa :
- Jika fungsi sinus
alt="y = f(x) = a \sin (bx + c) + d" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29+%3D+a+%5Csin+%28bx+%2B+c%29+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y = f(x) = a \sin (bx + c) + d" /> , maka nilai maksimumnyaalt="y_{maks} = \mid a\mid + d" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+%5Cmid+a%5Cmid+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = \mid a\mid + d" /> dan nilai minimumnyaalt="y_{min} = -\mid a\mid + d" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D+%3D+-%5Cmid+a%5Cmid+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y_{min} = -\mid a\mid + d" /> - Jika fungsi kosinus
alt="y = f(x) = a \cos (bx + c) + d" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29+%3D+a+%5Ccos+%28bx+%2B+c%29+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y = f(x) = a \cos (bx + c) + d" /> , maka nilai maksimumnyaalt="y_{maks} = \mid a\mid + d" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+%5Cmid+a%5Cmid+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = \mid a\mid + d" /> dan nilai minimumnyaalt="y_{min} = -\mid a\mid + d" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D+%3D+-%5Cmid+a%5Cmid+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y_{min} = -\mid a\mid + d" /> -
Jika
alt="y = f(x)" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29&bg=f9f9f9&fg=000000&s=0" title="y = f(x)" /> adalah fungsi periodik dengan nilai maksimumalt="y_{maks}" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D&bg=f9f9f9&fg=000000&s=0" title="y_{maks}" /> dan minimumalt="y_{min}" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D&bg=f9f9f9&fg=000000&s=0" title="y_{min}" /> , maka amplitudonya adalah :
Jenis Grafik Fungsi Trigonometri
1. Grafik fungsi baku alt="f(x) = \sin x" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+%5Csin+x&bg=f9f9f9&fg=000000&s=0" title="f(x) = \sin x" /> ; alt="f(x) = \cos x" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+%5Ccos+x&bg=f9f9f9&fg=000000&s=0" title="f(x) = \cos x" /> ; dan alt="f(x) = \tan x" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+%5Ctan+x&bg=f9f9f9&fg=000000&s=0" title="f(x) = \tan x" />
Sinus
Cosinus
Tangen
2. Grafik fungsi alt="f(x) = a\sin x" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+a%5Csin+x&bg=f9f9f9&fg=000000&s=0" title="f(x) = a\sin x" /> ; alt="f(x) = a\cos x" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+a%5Ccos+x&bg=f9f9f9&fg=000000&s=0" title="f(x) = a\cos x" /> ; dan alt="f(x) = a\tan x" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+a%5Ctan+x&bg=f9f9f9&fg=000000&s=0" title="f(x) = a\tan x" />
Didapat dari grafik trigonometri baku dengan cara mengalikan koordinat setiap titik pada grafik baku dengan bilangan a, sedangkan absisnya tetap. Periode grafik tetap
Sinus
Misalkan
Kosinus
Misalkan
Tangen
Misalkan
3. Grafik fungsi alt="f(x) = a\sin kx" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+a%5Csin+kx&bg=f9f9f9&fg=000000&s=0" title="f(x) = a\sin kx" /> ; alt="f(x) = a\cos kx" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+a%5Ccos+kx&bg=f9f9f9&fg=000000&s=0" title="f(x) = a\cos kx" /> ; dan alt="f(x) = a\tan kx" src="https://s0.wp.com/latex.php?latex=f%28x%29+%3D+a%5Ctan+kx&bg=f9f9f9&fg=000000&s=0" title="f(x) = a\tan kx" />
Didapat dari grafik trigonometri baku dengan cara mengalikan ordinat setiap titik pada grafik baku dengan bilangan a, sedangkan periode grafik sinus dan kosinus menjadi :
Dan tangen
- Sinus
Misalkan
- Kosinus
Misalkan
- Tangen
Misalkan a=1
- Jika fungsi kosinus
alt="y = f(x) = a \cos (bx + c) + d" src="https://s0.wp.com/latex.php?latex=y+%3D+f%28x%29+%3D+a+%5Ccos+%28bx+%2B+c%29+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y = f(x) = a \cos (bx + c) + d" /> , maka nilai maksimumnyaalt="y_{maks} = \mid a\mid + d" src="https://s0.wp.com/latex.php?latex=y_%7Bmaks%7D+%3D+%5Cmid+a%5Cmid+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y_{maks} = \mid a\mid + d" /> dan nilai minimumnyaalt="y_{min} = -\mid a\mid + d" src="https://s0.wp.com/latex.php?latex=y_%7Bmin%7D+%3D+-%5Cmid+a%5Cmid+%2B+d&bg=f9f9f9&fg=000000&s=0" title="y_{min} = -\mid a\mid + d" />
Jika
Dengan demikian, fungsi sinus