Maths

This is a Objective Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l}Here,aRb\Rightarrow aisabrotherofb.\\ aRa\Rightarrow aisabrotherofawhichisnottrue.\\ So,Risnotreflexive.\\ aRb\Rightarrow aisabrotherofb.\\ bRa\Rightarrow whichisnottruebecausebmaybesisterofa.\\ \Rightarrow aRb\ne bRa\\ So,Risnotsymmetric.\\ Now,aRb,bRc\Rightarrow aRc\\ \Rightarrow aisthebrotherofbandbisthebrotherofc.\\ \therefore aisalsothebrotherofc.\end{array}$

This is a Objective Type Question as classified in NCERT Exemplar

Sol:$\begin{array}{l}\end{array}$

$\begin{array}{l}Ifa=b\forall a,b\in T\\ thenaRa\Rightarrow a\cong awhichistrueforalla\in T\\ So,Risreflexive\\ Now,aRbandbRa.\\ i.e.,a\cong bandb\cong awhichistrueforalla\in T\\ Rissymmetric.\\ LetaRbandbRc.\\ \Rightarrow a\cong bandb\cong a\Rightarrow a\cong c\forall a,b,c\in T\\ So,Ristransitive.\\ Hence,Risequivalencerelation.\\ So,thecorrectansweris(c).\end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:$\begin{array}{l}\begin{array}{l}\begin{array}{l}\begin{array}{l}\hfill \end{array}\end{array}\hfill \end{array}\end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l}f(x)\frac{1}{2-cosx},\forall x\in R\\ Rangeofcosxis[-1,1]\\ Letf(x)=y=\frac{1}{2-cosx}\\ \Rightarrow 2y-ycosx=1\Rightarrow ycosx=2y-1\\ \Rightarrow cosx=\frac{2y-1}{y}=2-\frac{1}{y}\\ Now-1\le cosx\le 1\\ \Rightarrow -1\le 2-\frac{1}{y}\le 1\Rightarrow -1-2\le -\frac{1}{y}\le 1-2\\ \Rightarrow -3\le -\frac{1}{y}\le -1\Rightarrow 3\ge \frac{1}{y}\ge 1\Rightarrow \frac{1}{3}\le y\le 1\\ \therefore therangeoff=\left[\frac{1}{3},1\right].\end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{}\end{array}Let{x}_1,x_2\in gof$

$gof\{f(x_1)\}=gof\{f(x_2)\}$

$\Rightarrow g(x_1)=g(x_2)\begin{array}{l} \end{array}$

$\therefore$
$\begin{array}{l}{x}_1 =x_2\\ \end{array}$

$\begin{array}{l}Hence,fisone-oneandgisonto.\end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$Giventhat,$

$\begin{array}{l}X=\{1,2,3\}andY=\{4,5\}\hfill \end{array}$

$\begin{array}{l}\therefore X *\text{?}Y=\{(1,4),(1,5),\left(2,4\right),\left(2,5\right),(3,4),(3,5)\}\hfill \end{array}$

$\begin{array}{l}\left(i\right)f=\{(1,4),\left(1,5\right),\left(2,4\right),(3,5)\}\hfill \end{array}$

$\begin{array}{l}fisnotafunctionbecausefhasnouniqueimage.\hfill \end{array}$

$\begin{array}{l}\left(ii\right)g=\left\{\left(1,4\right),\left(2,4\right),\left(3,4\right)\right\}\hfill \end{array}$

$\begin{array}{l}Since,gisafunctionaseachelementofthedomainhasauniqueimage.\hfill \end{array}$

$\begin{array}{l}\left(iii\right)h=\{(1,4),(2,5),(3,5)\}\hfill \end{array}$

$\begin{array}{l}Itisafunctionaseachelementofthedomainhasauniqueimage.\hfill \end{array}$

$\begin{array}{l}\left(iv\right)k=\{(1,4),\left(2,5\right)\}\hfill \end{array}$

$\begin{array}{l}kisnotafunctionas3doesnothaveanyimageunderthemapping.\hfill \end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l}Givenfunction,f(x)=cosx\forall x\in R\\ Let\left[-\frac{\pi }{2},\frac{\pi }{2}\right]\in f(x)\\ f\left(-\frac{\pi }{2}\right)=cos\left(-\frac{\pi }{2}\right)=cos\frac{\pi }{2}=0\\ cos\left(\frac{\pi }{2}\right)=cos\frac{\pi }{2}=0\\ But-\frac{\pi }{2}\ne \frac{\pi }{2}\\ \therefore ,f(x)isnotone-one.\\ Now,f(x)=cosx,\forall x\in Risnotontoasthereisnopre-imageforanyrealnumber.\\ Whichdoesnotbelongtotheintervals[-1,1],therangeofcosx.\end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l}f(z)=\left|z\right|\forall z\in C\\ f(1)=\left|1\right|=1\\ f(-1)=\left|-1\right|=1\\ f(1)=f(-1)\\ But1\ne -1\\ Therefore,itisnotone-ono.\\ Now,letf(z)=y=\left|z\right|.\\ Here,thereisno;pre-imageofnegativenumbers.\\ Hence,itisnotonto.\end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$Given that,$
$\begin{array}{l}f = \left\{\left(1,2\right),\left(3,5\right),\left(4,1\right)\right\}\hfill \end{array}$

$and$
$\begin{array}{l}g = \left\{\left(2,3\right),\left(5,1\right),\left(1,3\right)\right\}\hfill \end{array}$

$\begin{array}{l}Now, fog \left(2\right) = f \left\{g\left(2\right)\right\} = f \left(3\right) = 5\hfill \end{array}$

$\begin{array}{l}fog \left(5\right) = f \left\{g\left(5\right)\right\} = f \left(1\right) = 2\hfill \end{array}$

$\begin{array}{l}fog \left(1\right) = f \left\{g\left(1\right)\right\} = f \left(3\right) = 5\hfill \end{array}$

$\begin{array}{l}fog = \left\{\left(2,5\right),\left(5,2\right),\left(1,5\right)\right\}\hfill \end{array}$

This is a Short Answer Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l}\left(i\right)Given set of ordered pair is \left\{\left(x,y\right):xisaperson,yisthemotherofx\right\}.\hfill \end{array}$$\begin{array}{l}It represents a function.\hfill \end{array}$

$\begin{array}{l}Here, the image of distinct elements of x under f are not distinct, so it is not an injective but it is a surjective.\hfill \end{array}$

$\begin{array}{l}\left(ii\right)Set of ordered pairs = \left\{\left(a,b\right):aisaperson,bisanancestorofa\right\}\hfill \end{array}$

$\begin{array}{ll}Here, each element of domain does not have a unique image.\hfill & \hfill \end{array}$

$\begin{array}{l}So, it does not represent function.\hfill \end{array}$