• Support PF! Buy your school textbooks, materials and every day products Here!

Integration with trig functions

  • Thread starter eaglesfn68
  • Start date
  • #1

Homework Statement



integral of x^2/sqrt(9-25x^2)

Homework Equations





The Attempt at a Solution



dont know how to type theta so im using @

so i made x=3sin@
dx=3cos@d@

sqrt(9-25x^2)=sqrt(9-25(sin^2@))=sqrt(9-225(sin^2@)=sqrt(9(1-25(sin^2@))=sqrt(9(1-25(1-cos^2@))

not sure if im supposed to make sin^2 into cos^2 -1 or not and not sure were to go next
 

Answers and Replies

  • #2
dextercioby
Science Advisor
Homework Helper
Insights Author
12,985
540
You want to have 9-25x^2 = C(1-sin^2 t). What's x(t) and what's C equal to ?

Sin/Cos as substitutions for sqrt(a-bx^2) work equally as well as tanh.
 

Related Threads on Integration with trig functions

  • Last Post
Replies
1
Views
1K
Replies
3
Views
4K
  • Last Post
Replies
3
Views
6K
Replies
4
Views
2K
Replies
4
Views
5K
Replies
8
Views
1K
Replies
5
Views
4K
Replies
1
Views
1K
Replies
5
Views
4K
Replies
15
Views
3K
Top