Another Trigonometric Integral Problem Help Me

  • #1

Homework Statement


∫sec^2 (x) * tan (x) dx


Homework Equations


sec^2 (x)= 1+tan^2(x)


The Attempt at a Solution


=∫(1+tan^2 (x) or tan (x) tan (x)) tan (x) dx u=tan x, du=sec^2 dx

∫ (1+u^2) u du

= ∫u+u^2)du
= u^2/2 + u^3/3 = 1/2 tan^2(x)+ 1/3 tan^3 (x) +c

the answer in the back of the book is 1/2 tan^2(x)+c

what did i do wrong
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,223
31
You didn't need to use this identity: sec2 (x)= 1+tan2(x)

u=tan x, du=sec^2 dx <-- This is an ideal start

[tex]\int tan(x) (sec^2(x) dx)[/tex]



Do you see where to replace your tan(x) as u and so on now?
 

Related Threads on Another Trigonometric Integral Problem Help Me

  • Last Post
Replies
5
Views
1K
  • Last Post
Replies
2
Views
1K
Replies
2
Views
836
Replies
1
Views
386
  • Last Post
Replies
1
Views
909
Replies
1
Views
1K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
4
Views
902
Replies
3
Views
1K
Top