Question

integrate (x)(cos^3 x) dx

Answer 1

do you know the reduction formula for \[\int \cos^n x \,\mathrm dx\]

Answer 2

reduction?? nope...

Answer 3

first simplify cos^3 x in terms of cosine of 3x and x
and then integrate by parts

Answer 4

i don't think here u should use reduction formula

Answer 5

its \[\cos ^3 x\] .. where did u get 3x and x @matricked

Answer 6

use
cos3x =4 cos^3 (x) - 3cos x

Answer 7

why not? it solves the problem too, but the solution may not be attractive to @bii17

Answer 8

i mean use cos^3 (x) =1/4 *(cos3x +3cosx)

Answer 9

oh okay.. then what will happen next ? @matricked

Answer 10

and then use by parts

Answer 11

\[1/4 [x(\cos 3x + 3\cos x)]dx\] is this correct? @matricked

Answer 12

yup

Answer 13

so there will be u and du den dv and v... i used Dv as cos 3x dx the V will be 1/3 sin 3x ???

Answer 14

for both integration of 1/4 *xcos3x take x as the first function

Answer 15

i get it.. thanks a lot :) @matricked