Integration with trig functions

  • Thread starter eaglesfn68
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  • #1
eaglesfn68
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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
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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.
 

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