WISKUNDE
Graad 11
NOG OEFENINGE
Grafieke van die trigonometriese funksies, sin, cos, tan : antwoorde.
  
  
Antwoorde  1
    
$$ \hspace*{2 mm}\mathrm{1.1\kern3mmy = 2\ sin\ x\ − 1\kern2mm\ } $$
           Vertikale translasie : q = minus; 1 and
           Die grafiek wissel/ossileer/swaai om y = minus; 1.
           amplitude = 2
           maksimum = 2 − 1 = 1
           minimum = − 2 − 1 = − 3
           Periode = 360°
           Die maksimum word bereik
           by x = 90° en x = -270°
           Die minimum word bereik
           x = − 90° en x = 270°

                                                                   [ V 1.1 ]
    
$$ \hspace*{2 mm}\mathrm{1.2\kern3mmy = 1 − 2 sin\ x\kern2mm\ } $$
           Vertikale translasie : q = 1 and
           Die grafiek wissel om y = 1.
           amplitude = 2
           maksimum = 2 + 1 = 3
           minimum = − 2 + 1 = − 1
           Periode = 360°
           Die maksimum word bereik
           by x = − 270° en x = 90°
           Die minimum word bereik
           by x = −270° en x = 90°

                                                                   [ V 1.2 ]
    
$$ \hspace*{2 mm}\mathrm{1.3\kern3mmy = 2\ cos\ x\ − 1\kern2mm\ } $$
           Vertikale translasie : q = − 1 and
           Die grafiek wissel om y = − 1.
           amplitude = 2
           maksimum = 2 − 1 = 1
           minimum = − 2 − 1 = − 3
           Periode = 360°
           Die maksimum word bereik
           by x = − 360°; x = 0° en x = 360°
           Die minimum word bereik
           by x = −180° en x = 180°

                                                                   [ V 1.3 ]
    
$$ \hspace*{2 mm}\mathrm{1.4\kern3mmy = 1 − 2\ cos\ x\kern2mm\ } $$
           Vertikale translation : q = 1
           Die grafiek swaai om y = 1.
           amplitude = 2
           maksimum = 3
           minimum = − 1
           Periode = 360°
           Die maksimum word bereik
           by x = − 180° en x = 180°
           Die minimum word bereik
           by x = −360°; x = 0° en x = 360°

                                                                   [ V 1.4 ]
    
$$ \hspace*{2 mm}\mathrm{1.5\kern3mmy = sin\ (x − 30°)\kern2mm\ } $$
           Vertikale translasie : q = 0
           Die grafiek ossilleer om y = 0, die X-as.
           amplitude = 1
           max\ksimum = 1
           minimum = − 1
           Periode = 360°
           Die maksimum word bereik
           by x = − 240° en x = 120°
           Die minimum word bereik
           at x = −60°; x = 0° and x = 300°

                                                                   [ V 1.5 ]
    
$$ \hspace*{2 mm}\mathrm{1.6\kern3mmy = sin\ (x + 60°)\kern2mm\ } $$
           Vertikale translasie : q = 0
           Die grafiek ossilleer om y = 0, die X-as.
           amplitude = 1
           maksimum = 1
           minimum = − 1
           Periode = 360°
           Die maksimum word bereik
           by x = − 330° en x = 300°
           Die minimum word bereik
           by x = −150°; en x = 210°

                                                                   [ V 1.6 ]
    
$$ \hspace*{2 mm}\mathrm{1.7\kern3mmy = cos\ (x − 60°)\kern2mm\ } $$
           Vertikale translasie : q = 0 and
           Die grafiek wissel om y = 0, die X-as.
           amplitude = 1
           maksimum = 1
           minimum = − 1
           Periode = 360°
           Die maksimum word bereik
           by x = − 300° en x = 60°
           Die minimum word bereik
           by x = −120°; en x = 240°

                                                                   [ V 1.7 ]
    
$$ \hspace*{2 mm}\mathrm{1.8\kern3mmy = cos\ (x + 30°)\kern2mm\ } $$
           Vertikale translasie : q = 0
           Die grafiek wissel om y = 0, die X-as.
           amplitude = 1
           maksimum = 1
           minimum = − 1
           Periode = 360°
           Die maksimum word bereik
           aby x = − 30° en x = 330°
           Die minimum word bereik
           by x = −210°; en x = 150°

                                                                   [ V 1.8 ]
    
$$ \hspace*{2 mm}\mathrm{1.9\kern3mmy = 1 − sin x\kern2mm\ } $$
           Vertikale translasie : q = 1
           Die grafiek wissel om y = 1.
           amplitude = 1
           maksimum = 2
           minimum = 0
           Periode = 360°
           Die maksimum word bereik by x = − 90°
           Die minimum word bereik by x = 90°
                                                                   [ V 1.9 ]
    
$$ \hspace*{2 mm}\mathrm{1.10\kern3mmy = 3\ cos\ x\ − 2\kern2mm\ } $$
           Vertikale translasie : q = − 2
           Die grafiek ossilleer om y = −2.
           amplitude = 3
           maksimum = 3 × 1 − 2 = 1
           minimum = 3 × −1 − 2 = −5
           Periode = 360°
           Die maksimum word bereik by x = 0°
           Die minimum word bereik
           by x = − 180° en x = 180°
                                                                   [ V 1.1 ]
    
$$ \hspace*{2 mm}\mathrm{1.11\kern3mmy = sin\ (x − 30°)\kern2mm\ } $$
           Vertikale translasie : q = 0
           Die grafiek wissel om y = 0, die X-as.
           amplitude = 1
           maksimum = 1
           minimum = −1
           Periode = 360°
           Die maksimum word bereik by x = 60°
           Die minimum word bereik by x = − 120°
                                                                   [ V 1.11 ]
    
$$ \hspace*{2 mm}\mathrm{1.12\kern3mmy = cos\ (2x − 60°)\kern2mm\ } $$
$$ \hspace*{12 mm}\mathrm{y = cos\ 2(x − 30°)\kern2mm\ } $$
           Vertikale translasie : q = 0
           Die grafiek ossilleer om y = 0, die X-as.
           amplitude = 1
           maksimum = 1
           minimum = −1
$$ \hspace*{9 mm}\mathrm{Periode\ = \Big(\frac{360}{2}\Big)^{°} = 180°\kern2mm\ } $$

           Die maksimum word bereik
           by x = −150° en x = 30°
           Die minimum word bereik
           by x = − 60° en x = 120°
                                                                   [ V 1.12 ]
    
$$ \hspace*{2 mm}\mathrm{1.13\kern3mmy = cos\ (x + 30°)\ − 1\kern2mm\ } $$
           Vertic\kale translasie : q = − 1
           Die grafiek ossilleer om y = −1.
           amplitude = 1
           maksimum = 1 − 1 = 0
           minimum = −1 −1 = −2
           k = 1 en periode = 360°
           Horisontale translasie : p = 30° na links
           Die maksimum word bereik by x = −30°
           Die minimum word bereik by x = 150°
                                                                   [ V 1.13 ]
    
$$ \hspace*{2 mm}\mathrm{1.14\kern3mmy = sin\ (x + 60°)\ + 1\kern2mm\ } $$
           Vertikale translasie : q = 1
           Die grafiek wissel om y = 1.
           amplitude = 1
           maksimum = 1 + 1 = 2
           minimum = 1 − 1 = 0
           k = 1 en die periode = 360°
           Horisontale verskuiwung : p = 60° na links
           Die maksimum word bereik by x = 30°
           Die minimum word bereik by x = −150°
                                                                   [ V 1.14 ]
    
$$ \hspace*{2 mm}\mathrm{1.15\kern3mmy = tan\ x\kern2mm\ } $$
           Asimptote by x = -90° en x = 90°
           Periode = 180°
           tan x = 1 by x = -135° en x = 45°.
           tan x = − 1 by x = -45° en by x = 135°
           Grafiek is stygend.
                                                                   [ V 1.15 ]
    
$$ \hspace*{2 mm}\mathrm{1.16\kern3mmy = tan\ x +\ 1\kern2mm\ } $$
           Asimptote by x = -90° en x = 90°
           Periode = 180°
           Vertikal verskuiwing : q = 1
           tan x = 1 by x = 0°.
           Grafiek is stygend.
                                                                   [ V 1.16 ]
    
$$ \hspace*{2 mm}\mathrm{1.17\kern3mmy = tan\ (x + 30°)\kern2mm\ } $$
           Asimptote by x = -120° en x = 60°
           Periode = 180°
           Vertikal translasie : q = 0
           Horisontale verskuiwing : p = 30° na links
           tan x = 1 by x = −165° ; x = 15°.
           Grafiek is stygend.
                                                                   [ V 1.17 ]
    
$$ \hspace*{2 mm}\mathrm{1.18\kern3mmy = tan\ 2x\kern2mm\ } $$
           Asimptote by x = -45° en x = 45°
           Periode = 90°
           Vertikale translasie : q = 0
           Horisontale verskuiwing : p = 0°
           tan x = 1 by x = &inus;1650° en x = 150°.
           Grafiek is stygend.
                                                                   [ V 1.18 ]
  
Antwoorde  2
2.1   The graph of y = a  sin k(x + p)
    
$$ \hspace*{2 mm}\mathrm{2.1\kern3mmy = a\ sin\ k(x + p)\ +\ q\kern2mm\ } $$
           Die grafiek ossilleer om y = 0, die
           X-as en dus q = 0..
           Amplitude = 1 sodat a = 1.
$$ \hspace*{9 mm}\mathrm{periode\ = 180°\ en\ k = \Big(\frac{360°}{180°}\Big) = 2\kern2mm\ } $$

           Horisontale translasie is 30° na links; p = +30°
           Vergelyking : y = 1.sin 2x + 30°
                                       = sin 2(x + 15)°                    [ V 2.1 ]
    
$$ \hspace*{2 mm}\mathrm{2.2\kern3mmy = a\ cos\ k(x + p)\ +\ q\kern2mm\ } $$
           Die grafiek wissel om y = 0, th\\die
           X-axs en dus q = 0..
           Amplitude = 1 sodat a = 1.
$$ \hspace*{9 mm}\mathrm{periode\ = 120°\ en\ k = \Big(\frac{360°}{120°}\Big) = 3\kern2mm\ } $$

           Horisontale translasie is 30° na regs; p = − 30°
           Vergelyking : y = 1.sin 2x − 30°
                                  = sin 2(x − 15)°                    [ V 2.2 ]
    
$$ \hspace*{2 mm}\mathrm{2.3\kern3mmy = a\ sin\ k(x + p)\ +\ q\kern2mm\ } $$
           Die grafiek ossilleer om y = 0, die
           X-axis en dus q = 0.
           Amplitude = 2 sodat a = 2.
$$ \hspace*{9 mm}\mathrm{periode\ = 120°\ en\ k = \Big(\frac{360°}{120°}\Big) = 3\kern2mm\ } $$

           By A(20° ; 0) : 3(20° + p) = 0°
                                       60° + 3p = 0°
                                                   p = − 20°
           Vergelyking : y = 2 sin 3(x − 20°)                   [ V 2.3 ]
    
$$ \hspace*{2 mm}\mathrm{2.4\kern3mmy = a\ cos\ k(x + p)\ +\ q\kern2mm\ } $$
           Die grafiek wissel om y = 0, die
           X-as en dus q = 0..
           Amplitude = 3 en die grafierk is 'n cosinus grafiek
           sodat a = −3.
$$ \hspace*{9 mm}\mathrm{periode\ = 180°\ en\ k = \Big(\frac{360°}{180°}\Big) = 2\kern2mm\ } $$

           By A(15° ; 0) : 2(15° + p) = 90°
                                       30° + 2p = 90°
                                                   p = 30°
           Vergelyking : y = − 3 cos 2(x + 30°)               [ V 2.4 ]
    
$$ \hspace*{2 mm}\mathrm{2.5\kern3mmy = a\ sin\ k(x + p)\ +\ q\kern2mm\ } $$
           Die grafiek ossilleer om y = − 2,
           en dus q = − 2.
           Amplitude = 3 sodat a = 3.
           Periode = 360° en k = 1
           Daar is geen horisontale translasie nie en p = 0
           Vergelyking : y = 3 sin (x + 0°) − 2
                                       = 3 sin x − 2                           [ V 2.5 ]
    
$$ \hspace*{2 mm}\mathrm{2.6\kern3mmy = a\ cos\ k(x + p)\ + q\kern2mm\ } $$
           Die grafiek wissel om y = − 2,
           en dus q = − 2.
           Amplitude = 3 sodat a = 3.
$$ \hspace*{9 mm}\mathrm{periode\ = 180°\ en\ k = \Big(\frac{360°}{180°}\Big) = 2\kern2mm\ } $$

           Daar is geen horisontale translasie en p = 0°
           Vergelyking : y = 3 cos 2(x + 0°) − 2
                                       = 3 cos 2x − 2                     [ V 2.6 ]
  
Antwoorde  3
    
       3.1  A(− 150°;0);  B(30°;0);   C(0;− 0,5)            [ V 3.1 ]
    
$$ \hspace*{2 mm}\mathrm{3.2\kern3mmperiod = 360°\kern2mm\ } $$                                          [ V 3.2 ]
    
$$ \hspace*{2 mm}\mathrm{3.3\kern3mmsin\ (x - 30°) = cos\ 2x\kern2mm\ } $$
$$ \hspace*{29 mm}\mathrm{= sin\ (90° − 2x)\kern2mm\ } $$
$$ \hspace*{17 mm}\mathrm{x − 30° = 2x + n.360°\kern2mm\ } $$
$$ \hspace*{26 mm}\mathrm{x = 40° + n.120°;\ \ n \isin Z\kern2mm\ } $$
$$ \hspace*{33 mm}\mathrm{\bold{OF}\kern2mm\ } $$
$$ \hspace*{17 mm}\mathrm{x − 30° = 180° − (90° − 2x) + n.360°\kern2mm\ } $$
$$ \hspace*{17 mm}\mathrm{x − 30° = 180° − 90° + 2x + n.360°\kern2mm\ } $$
$$ \hspace*{23 mm}\mathrm{− x = 120° + n.360°\kern2mm\ } $$
$$ \hspace*{24 mm}\mathrm{ x = −120° − n.360°\kern2mm\ } $$
           Oplossing : x = 40°−1.120° ;  40° + 0.120° ;
                             x = 40° + 1.120° and − 120° − 0.360°;
           Oplossing : x = − 80°(E); 40°(F); 160°(G) ; − 120°(D)
                                                                                [ V 3.3 ]
    
$$ \hspace*{2 mm}\mathrm{3.4\kern3mmf(x) < − 0,5\ \ as\ − 120° < x < 0°\kern2mm\ } $$          [ V 3.4 ]
    
$$ \hspace*{2 mm}\mathrm{3.5\kern3mmf(x) ≥ 0,5\ \ as\ 60° ≤ x ≤ 180°\kern2mm\ } $$               [ V 3.5 ]
  
Antwoorde  4
     4.1  f:  amplitude = 2 en dus a = 2
          Die kosinusgrafiek bereik 0 by 60° in plaas
          van by 90° sodat die grafiek dus 30° na links
          verskuif is en dus b = 30°
          Die sinusgrafiek, g, ossilleer om y = 1
          sodat c = 1
$$ \hspace*{8 mm}\mathrm{periode = 180°\ en\ dus\ d = \Big(\frac{360°}{180°}\Big) = 2\kern2mm\ } $$
                                                                                [ V 4.1 ]
    
$$ \hspace*{2 mm}\mathrm{4.2\kern3mmf(x) = 2\ cos\ (x − 30°)\kern2mm\ } $$
$$ \hspace*{10 mm}\mathrm{f(0) = 2\ cos\ (0 + 30°)\kern2mm\ } $$
$$ \hspace*{16 mm}\mathrm{= 2\ cos\ 30°\kern2mm\ } $$
$$ \hspace*{16 mm}\mathrm{= 2\Big(\frac{\sqrt3}{2}\Big) = \sqrt3\kern2mm\ } $$                             [ V 4.2 ]


     4.3.1  f:  x = 45° en x = −135°                         [ V 4.3.1 ]

     4.3.2  f en g kruis by (−90° ; 1) en
               by (13,5° ; 1,45): dus die oplossing :
               −90° ≤ x ≤ 13,5°                                   [ V 4.3.2 ]

     4.4  f(x) bereik sy maksimum by − 30°.
            Die as is dus 30° na links verskuif,
            d.i die grafiek is 30° na regs verskuif
            en p = 30°
$$ \hspace*{10 mm}\mathrm{f(x) = 2 cos (x − 30°)\kern2mm\ } $$
$$ \hspace*{10 mm}\mathrm{f(x) = 2 cos (x + 30° − 30°)\kern2mm\ } $$
$$ \hspace*{10 mm}\mathrm{f(x) = 2 cos x\kern2mm\ } $$                                          [ V 4.4 ]
  
Antwoorde  5
     5.1  f:  amplitude = 1 en dus a = 1
          Die kosinusgrafiek bereik 1 by 30° i.p.v.
          0° sodat die grafiek 30° na regs
          verskuif is en dus b = −30°
          Die sinusgrafiek, g, het 'n periode = 360°
          sodat c = 1
                                                                                [ V 5.1 ]
    
$$ \hspace*{2 mm}\mathrm{5.2.1\kern3mmOmvang\ :\ −0,5 \le y \le 1\kern2mm\ } $$                [ V 5.2.1 ]
    
$$ \hspace*{2 mm}\mathrm{5.2.2\kern3mm30° < x \le 90°\kern2mm\ } $$                                    [ V 5.2.2 ]
  
$$ \hspace*{2 mm}\mathrm{5.2.3\kern3mmOmvang : −90° ≤ x ≤ −60°\ \ en\ \ x = 0°\kern2mm\ } $$
                                                                                [ Q 5.2.3 ]
    
$$ \hspace*{2 mm}\mathrm{5.3\kern3mmcos\ (x − 30°)\ =\ sin\ x\kern2mm\ } $$
$$ \hspace*{31 mm}\mathrm{= cos\ (90° − x)\kern2mm\ } $$
$$ \hspace*{16 mm}\mathrm{\therefore x − 30° = 90° − x + n\bold{.}360°\ \kern3mm\ n ∈ Z\kern2mm\ } $$
$$ \hspace*{23 mm}\mathrm{\therefore 2x = 120° + n\bold{.}360°\kern2mm\ } $$
$$ \hspace*{25 mm}\mathrm{\therefore x = 60° + n\bold{.}180°\kern2mm\ } $$
$$ \hspace*{25 mm}\mathrm{\therefore x = 60°\kern2mm\ } $$
          As g(x) > f(x) dan 60° < x ≤ 90°                [ V 5.3 ]


     5.4  Die grafiek van g(x) is 60° na links
            verskuif en dus verander x na x + 60°
$$ \hspace*{10 mm}\mathrm{g(x) = sin x\kern2mm\ } $$
$$ \hspace*{10 mm}\mathrm{h(x) = sin (x + 60°)\kern2mm\ } $$                               [ V 5.4 ]


     5.5  f(x) moet 60° na regs verskuif word
            om g(x) te vorm.                                       [ V 5.5 ]

  
Antwoorde  6
     6.1  Amplitude = 2 en dus c = 2
            periode = 360° en dus d = 1.                     [ V 6.1 ]

     6.2  Amplitude = 1 en dus a = 1;
            f(60°) = 1 en dus is die grafiek 60° na regs
            verskuif sodat b = − 60°                             [ V 6.2 ]

     6.3  Reikwydte : − 2 ≤ y ≤ 2                            [ V 6.3 ]

     6.4  −120° ≤ x ≤ − 30°                                       [ V 6.4 ]

     6.5  Die Y-as is 30° na links verskuif sodat die
            oorspronklike sinusgrafiek 30° na regs
            verskuif is en x verander na x − 30°
            y = 2 sin x word y = 2 sin (x − 30°).
                                                                                   [ V 6.5 ]

  
Antwoorde  7
     7.1  Die grafiek van sin x = 0 by 0°
            g(x) = 0 by − 30°. g(x) is dus 30° na links
            verskuif en dus b = 30°.                           [ V 7.1 ]

     7.2  Periode = 360°                                             [ V 7.2 ]

     7.3  f(x) − g(x) = 0 by x = − 150° en
            x = 30°:                                                          [ V 7.3 ]

     7.4.1  sin (90° − x) = cos x, dus f(x) > g(x)
               x ∈ (− 150° ; 30°)                                      [ V 7.4.1 ]

     7.4.2  Vir f(x).g(x) < 0, moet f(x) en g(x) verskillende
               tekens hê. f(x) < 0 as x < − 90° en
               g(x) < 0 as x < − 30°. Dus f(x) en g(x) het
               verskillende tekens as −90° < x < −30°.
               Dus f(x).g(x) < 0 as −90° < x < −30°.
                                                                                [ V 7.4.2 ]

     7.4.3  f(x).g(x) ≥ 0 as −180° ≤ x ≤ −90° en
               −30° ≤ x ≤ 90°.                                     [ V 7.4.3 ]

     7.5  f(x) het 'n minimum van − 1 en 'n maksimum
            van 1. Alle y-waardes word met 3 vermeerder,
            sodat die reikwydte of omvang
            -1+3 ≤ y ≤ 1+3,    d.i. 2 ≤ y ≤ 4.
                                                                                [ V 7.5 ]

     7.6  f(x) word 3 eenhede afwaarts verskuif, sodat
            y = 0 − 3 = − 3. p(x) = cos x − 3                 [ V 7.6 ]

     7.7  f(x) word 30° na links verskuif, sodat
            p = 30°. Dus q(x) = cos (x − 30°)             [ V 7.7 ]