plz point out the mistake

integration

a.secx + b.cosecx dx
sinx + cosx

limits 0 to pi/2

awkwardly enuf i am getting 0 [11]

18 Answers

62
Lokesh Verma ·

PHilip.. you are makign the mistake of forgetting to take the limit...

you have to integrate from a to pi/2-a

and then take limit a going to 0

1
Philip Calvert ·

ok plz close this thread now the correct answer can be found using the method given by nishant bhaiyya above

and since my problem is actually something else altogether forget it and don't waste more time on it

hopefully i will find the "board" (read bored) method for it [6]

1
Honey Arora ·

itz a direct kind of ques.......

1
Philip Calvert ·

ya i tried doing all this bcoz i cud not think of any simpler method but since i never saw the use of limits in ISC board ques i am begining to believe i will have to something altogether different

btw if i used this method it will satisfy me but unfortunately i will get 0 in my paper

1
Honey Arora ·

∫cosecx is log (cosec x-cotx)

62
Lokesh Verma ·

philip i remember the limit thing that i am talking is in CBSE too....

62
Lokesh Verma ·

so how come u got the answer as zero.. can i see ur method?

1
Philip Calvert ·

can you explain a bit more celestine ?

bhaiyya but ye board ka question hai must be quite simpler

9
Celestine preetham ·

jus use that as cosec2x and integrate u wont get 0

1
Philip Calvert ·

replacing x → pi/2 -x
i get
Ï€/2
2I = (a+b)∫ (1/sinx.cosx) dx
0

is something wrong up till here [7]

62
Lokesh Verma ·

the integral does not become zero!

Does it!?

1
Honey Arora ·

hw cn u get ans by putting sin x =t?.....thn dt will be (cos x dx) bt it is in the deno.

1
skygirl ·

[3]

11
Anirudh Narayanan ·

Sky, not calculation mistake......it is calculus mistake [3]

1
Philip Calvert ·

shud i try it the long way......

by putting sinx =t ??

1
skygirl ·

oh no no...

calculation mistake!!

1
Honey Arora ·

i m also getting the same

1
skygirl ·

i dun think ..

i also thot the same thing b4 seeing ur soluntin.

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