Continuity

If f(x)=lim (sinx)2n,then f is
n→∞
A) conti. at x=Î /2
B) disconti at x=Î /2
C)disconti at x=Î
D) none of these

8 Answers

62
Lokesh Verma ·

hmm.. this is sort of simple... (Except that u must have n-> infinity!)

obvious point of contention is Pi/2

b is the correct choice..

can u make some guess why

33
Abhishek Priyam ·

yes b is right [1]............

i gussed [6]

1
naman_475 ·

yes ans is b ...but how?

62
Lokesh Verma ·

see at all points other than pi/2 the value of this function is less than 1

so what happens is that when you take the power to infinity it will tend to zero except at pi/2 where it is 1

so the limit of pi/2+ and pi/2- will be zero .. while at pi/2 it is 1..

hence the result..

1
skygirl ·

f(x)=lim n->∞ (sinx)^2n = f(x)=lim n->∞ [1- (1-sinx)]^(1/(1-sinx))2n(1-sinx)

now this thing... [1- (1-sinx)](1/(1-sinx))2n(1-sinx) will not be defined for sinx=1 i.e. x=pi/2

hence f(x) is discont at x=pi/2.

can we interpret it in this way??

1
skygirl ·

oh nooooooo
i am extremely sorry.......
have not seen that its n tends to infinity........ thot x tends to infinity......
sorry :(

62
Lokesh Verma ·

no dear i am afraid not...

the only thing to look at here is that it is some number smaller than 1 raised to the power infinity..
ur solution is not correct...

u have unfortunately complicated a simpler thing...

if u look carefully at the logic i gave..

and if u see ur logic.. u are saying that u divide and multiply by 1-sinx

i can do that for (1/2-sinx) and take 1/2-(1/2-sinx) in lower number.. that logic will work for 1/2 as well..

i dont know how to tell the flaw in ur logic :(

62
Lokesh Verma ·

okie.. :)

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