Flag Integral Calculus> please give me the solution for this ques...
question mark

please give me the solution for this question as soon as possible

sravan sarma , 10 Years ago
Grade 12
anser 2 Answers
Sumit Majumdar

Last Activity: 10 Years ago

Solution:
I = ∫ dx / (sinx + secx)

= ∫ [ cosx / (cosxsinx + 1) ] dx

= ∫ [2cosx / 2(cosxsinx + 1) ] dx

= ∫ [ ( cosx + cosx + sinx - sinx) / (2cosxsinx + 2) ] dx

= ∫ [ ( cosx + sinx) / (2cosxsinx + 2) ] dx + ∫ [ ( cosx - sinx) / (2cosxsinx + 2) ] dx

= - ∫ [ (cosx + sinx)/( -3 - 2cosxsinx + cos²x + sin²x ) ] dx + ∫ [ ( cosx - sinx) / (2cosxsinx + 1 + cos²x + sin²x ) ] dx

= - ∫ [ (cosx + sinx)/( -3 + (cosx - sinx)² ) ] dx + ∫ [ ( cosx - sinx)/ ( 1 + ( cosx + sinx)² ) ] dx

= - ∫ [ 1 /( -3 + (sinx - cosx )² ) ] d(sinx - cosx) + ∫ [ 1/ ( 1 + (sinx + cosx)² ) ] d(sinx + cosx)

= - ∫ [ 1/( -3 + (sinx - cosx )² ) ] d(sinx - cosx) + ∫ [ 1/ ( 1 + (sinx + cosx)² ) ] d(sinx + cosx)


= - ∫ [ 1/( -3 + t² ) ] dt + ∫ [ 1/ ( 1 + u² ) ] du

= ( 1/√3 ) ln | (t + √3) / (t - √3) | + arctgu + C

= ( 1/√3 ) ln | (sinx - cosx + √3) / (sinx - cosx - √3) | + arctg(sinx + cosx) + C
Thanks & Regards
Sumit Majumdar,
askIITians Faculty
Ph.D,IIT Delhi

Sumit Majumdar

Last Activity: 10 Years ago

Dear student,
We can have the following result:
\int \frac{dx}{sinx+secx}=\int \frac{cosx}{sin^{2}x+1}
Now if I asume, u = sinx, so we get:
\int \frac{cosx}{sin^{2}x+1}=\int \frac{du}{1+u^{2}}=tan^{-1}u=tan^{-1}\left (sinx \right )+c
Regards
Sumit

Provide a better Answer & Earn Cool Goodies

Enter text here...
star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments


Ask a Doubt

Get your questions answered by the expert for free

Enter text here...