Integral of

(tan x)1/2 + (cot x)1/2

.Q. Intergrate : √ (tanx) + √(cotx) 

ANS : I =  ∫  { √ (tanx) + √(cotx) } dx

Apply : tanx = sinx / cosx  and  cotx = cosx / sinx

=> ∫  { √ (sinx/ cosx) + √(cosx / sinx) } dx

=> ∫  { √ (sin2x) + √(cos2x) } dx  / √(cosx *sinx)

=>  ∫  ( sinx +  cosx )  dx / ( sinx cosx )

=> √2 * ∫  ( sinx +  cosx )  dx / ( 2 * sinx cosx )

=> √2 * ∫  ( sinx +  cosx )  dx / ( 1-1 + 2sinx cosx )

=> √2 * ∫  ( sinx +  cosx )  dx / ( 1- { 1 - 2 * sinx cosx} )

=> √2 * ∫  ( sinx +  cosx )  dx / ( 1- { sin2x +  cos2x - 2 * sinx cosx} )

=> √2 * ∫  ( sinx +  cosx )  dx / ( 1- { sinx - cosx}2  )

Let  t = sin x - cos x  =>  dt = (cosx + sinx ) dx  =>  dt  = (sinx + cosx) dx  

∴ √2 * ∫ dt ( 1- { t }2  )

Apply :  ∫ [1 /  √( 1- x2  ) ] dx  =  sin-1x + C

=>  √2 * sin-1t + C

∴ I = √2 * sin-1(sin x - cos x )+ C

Therefore : ∫  { √ (tanx) + √(cotx) } dx = √2 * sin-1(sin x - cos x )+ C

IF YOU ARE SATISFIED DO GIVE THUMBS UP.

  • 33

One approach for this question is given in the textbook itself as you would know.

Another method can be this..

I = ( tan x)1/2 + (cot x)1/2

I =   ( sinx / cosx )1/2 +  ( cosx / sinx ) 12

I = ( sinx + cosx ) / ( sinx cosx )1/2

take

sin x - cos x = t

cosx + sinx dx = dt

Also, sin2x + cos2x - 2sinx cosx= t2

-->  2sinx cosx = 1 - t2

Therefore,

I = 21/2 ( dt / ( 1 - t2)1/2 )

 

Now using the formula of under root a2 - x2  we can solve it.

  • 18

Hi!
blueflame_tripti correctly stated the method to solve the question.
Imad93 correctly answered the question
 
Good effort!
Your answers are really helpful to all the users of this community.
Keep writing!!!
 
Cheers!
 

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