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# Integrating sin squared x watch

1. why can't you make sinx=u and use this substitution to do it?
2. (Original post by runny4)
why can't you make sinx=u and use this substitution to do it?
Well, you'd get

There's the problem.
3. Hint: You may wish to consider the following trigonometric identity.

.
4. (Original post by Thediplomat56)
Attachment 473295

Sorry it's meant to be -1/4sin2theta
Don't post full solutions.
5. (Original post by Thediplomat56)
Attachment 473295

Sorry it's meant to be -1/4sin2theta
Edit: WHoops thought you were the OP. Stupid 16Characters.
6. (Original post by runny4)
why can't you make sinx=u and use this substitution to do it?
Well, what do you end up with when you try this?
7. (Original post by Indeterminate)
Well, you'd get

There's the problem.
why is that a problem?- you end up with something in terms of sin and cos
8. (Original post by davros)
Well, what do you end up with when you try this?
you end up with sin cubed x over 3cosx
9. (Original post by runny4)
you end up with sin cubed x over 3cosx
Presumably you had an integral of

The issue is that so you cannot treat it as a constant when integrating w.r.t u.
10. (Original post by 16Characters....)
Presumably you had an integral of

The issue is that so you cannot treat it as a constant when integrating w.r.t u.
ok thank you i thought that you could treat cosx as constant with respect to u and bring it to the front of the integral but obviously u can't.

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