NCERT Solutions class 12 Maths Exercise Miscellenous (Ex misc.) Chapter 5 Continuity and Differentiability


NCERT Solutions for Class 12 Maths Exercise Miscellenous Chapter 5 Continuity and Differentiability – FREE PDF Download

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NCERT Solutions for Class 12 Maths Chapter 5 Continuity and Differentiability Exercise Miscellenous (Ex Misc.)



Differentiate with respect to  the functions in Exercises 1 to 5.

1. 

Ans. Let  

 

  = 

 


2. 

 

Ans. Let  =  

 

 


3. 

 

Ans. Let ……….(i) 

 

 

  

 

 

 

 

* 


4. 

 

Ans. Let  =  

 


5. 

 

Ans. Let  

     [By Quotient Rule]

 

 dydx=2x+7.24x2.1212.cos1x22x+7×2(2x+7)dydx=−2x+7.24−x2.12−12.cos−1x22x+7×2(2x+7)

 

[14x22x+7+cos1x2(2x+7)32]−[14−x22x+7+cos−1×2(2x+7)32]


Differentiate with respect to  the functions in Exercises 6 to 11.

 

6. 

Ans. Let   ……….(i) 

Now, 

 = 

And 

 = 

 From eq. (i),  

  = 

 


7. 

 

Ans. Let  ……….(i) 

Taking log both sides, we get

  = 

 

 

 

=>1ydydx=logx1logx.1x+log(logx)1x=>1ydydx=logx1logx.1x+log(logx)1x

=>1ydydx=1x+log(logx)1x=>1ydydx=1x+log(logx)1x

=>1ydydx=[1+log(logx)x]=>1ydydx=[1+log(logx)x]

 


8.  for some constants  and 

 

Ans. Let  for some constants  and  

  

 

 

 dydx=(asinxbcosx)sin(acosx+bsinx)dydx=(asin⁡x−bcos⁡x)sin⁡(acos⁡x+bsin⁡x)


9. 

 

Ans. Let  ……….(i) 

Taking log Both Sides, we get

 

=>logy=(sinxcosx)log(sinxcosx)=>logy=(sinx−cosx)log(sinx−cosx)

=>  ddxlogy=(sinxcosx)ddxlog(sinxcosx)+log(sinxcosx)ddx(sinxcosx)ddxlog⁡y=(sin⁡x−cos⁡x)ddxlog⁡(sin⁡x−cos⁡x)+log⁡(sin⁡x−cos⁡x)ddx(sin⁡x−cos⁡x)

 

 

 

 

 


10.  for some fixed  and 

 

Ans. Let  

 

  …….(i)

Now taking ,  let  ……….(ii)

Taking log both sides, we get

  = 

 

 

  = 

 

 From eq. (ii),

 From eq. (i),

=> dydx=xx(1+logx)+axa1+axlogadydx=xx(1+log⁡x)+axa−1+axlog⁡a


11.  for 

 

Ans. Let  for  

Putting  and 

  ……….(i)

Now 

  = 

 

 

 

  ……….(ii)

Again  

 

 

 

 

  ……….(iii)

Putting the values from eq. (ii) and (iii) in eq. (i),


12. Find  if  and 

 

Ans. Given:      and  

 

and dxdt=10ddt(tsint)dxdt=10ddt(t−sint)

=>dxdt=10(1cost)=>dxdt=10(1−cos⁡t)

 


13. Find  if 

 

Ans. Given:      

 

 

 

 

= 0


14. If  for  prove that 

 

Ans. Given:  

 

Squaring both sides,We get

 

 

 

 

 

 

 

 

 dydx=(1+x)ddx(x)(x)ddx(1+x)(1+x)2dydx=(1+x)ddx(−x)−(−x)ddx(1+x)(1+x)2

=> dydx=(1+x)+x(1+x)2dydx=−(1+x)+x(1+x)2

     Proved.


15. If  for some  prove that  is a constant independent of a and b.

 

Ans. Given: ……….(i) 

 

 

  ……….(ii)

Again 

   [From eq. (ii)

 

 ……….(iii)

Putting values of  and  in the given expression,

 =  = 

which is a constant and is independent of  and 


16. If  with  prove that 

 

Ans. Given:  

 

 

 

 

 

   [Taking reciprocal]


17. If  and  find 

 

Ans. Given:  and  

Differentiating both sides with respect to 

and 

 

and 

 

and 

  and  

Now    

Again   = 

 = 


18. If  show that  exists for all real  and find it.

 

Ans. Given:  

Now, L.H.D. at 

 

 L.H.D. at  = R.H.D. at 

Therefore,  is differentiable at .

  

Now, L.H.D. at 

  =  = 

And R.H.D. at 

 

limx03x=0limx→0−−3x=0

 Again L.H.D. at  = R.H.D. at 


19. Using mathematical induction, prove that  for all positive integers 

 

Ans. Let  be the given statement in the problem. 

  …..(i)

 = ,

which is true as 

Now we suppose  is true.

  …….(ii)

To establish the truth of  we prove,

 

 

  

 

 

Therefore,  is true if  is true but  is true.

 By Principal of Induction  is true for all  N.


20. Using the fact that  and the differentiation, obtain the sum formula for cosines.

 

Ans. Given:      

Consider A and B as function of  and differentiating both sides w.r.t. 

  

 


21. Does there exist a function which is continuous everywhere but not differentiable at exactly two points?

 

Ans. Let us consider the function     

 is continuous everywhere but it is not differentiable at  and 


22. If  prove that 

 

Ans. Given:  

 


23. If  show that 

 

Ans. Given:      

 

 

 

Differentiating both sides with respect to 

 

       Proved.