# Integration by parts.

by annamariesmit
Tags: integration, parts
 P: 1 how would one integrate by parts the following: $$\int sin^2xdx$$ thanks!
 P: 1 hi use the fact that sin^2 x = (1-cos2x)/2 from the formula cos2x=1-2sin^2 x Tell me how you wrote that equation
 Sci Advisor HW Helper P: 4,739 [ tex]\int sin^2xdx[/tex ] Click on the image (equation) and the TeX code comes up. See also: http://www.physicsforums.com/showthread.php?t=8997 Aslo this is not a forum for homeworks, http://www.physicsforums.com/showthread.php?t=44101 Post questions regarding homework and similar in the homework section.
Math
Emeritus
Thanks
PF Gold
P: 39,323
Integration by parts.

 Quote by annamariesmit how would one integrate by parts the following: $$\int sin^2xdx$$ thanks!
Are you required to use integration by parts? As rsm said, there are simple and standard substitutions for $sin^2(x)$ and $cos^2(x)$.

If you are required to use integration by parts, then, since integration by parts requires a product, the obvious thing to do it write this as a product:
$$\int sin^2(x) dx= \int (sin(x))(sin(x) dx)$$
Let u= sin(x) and let dv= sin(x) dx. Then du= cos(x)dx and v= -cos(x)
$$\int sin^2 x dx= -sin(x)cos(x)+ \int cos^2(x) dx$$
Now do the same thing with that integral. Of course, what happens is you will get back to your original $\int sin^2(x) dx$- but with a lot of other things. Solve that equation algebraically for $\int sin^2(x)dx$

 Related Discussions Calculus & Beyond Homework 5 Calculus & Beyond Homework 1 Calculus 6 Calculus & Beyond Homework 1 Calculus & Beyond Homework 5