IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: Priya on May 27, 2009, 06:44:42 pm

Title: Pure Maths help (Trig Integrals)
Post by: Priya on May 27, 2009, 06:44:42 pm

Could you tell me what is the integral of sec x... Is it sec x+tan x +c or sec x*tan x
Is using secxtanx in this video http://www.youtube.com/watch?v=8CHHY-2Ctug&feature=related (http://www.youtube.com/watch?v=8CHHY-2Ctug&feature=related) @ 2.25 appropriate?

Pls reply...
Thanks for helping me out!

Title: Re: Pure Maths help (Trig Integrals)
Post by: astarmathsandphysics on May 27, 2009, 07:18:43 pm

It is ln(secx+tanx)

Title: Re: Pure Maths help (Trig Integrals)
Post by: Priya on May 27, 2009, 07:36:01 pm

Thank you!

And I was confusing integration with differentiation in that video. Understood it now... Thanks again!!

Title: Re: Pure Maths help (Trig Integrals)
Post by: astarmathsandphysics on May 27, 2009, 07:38:34 pm

Multiply tanx by (tanx+secx)/(secx+tanx) and expand the brackets. Top is derivative of bottom so substittu u=(tanx+secx) to get du/u then integrate