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October 22, 2014

October 22, 2014

Posted by **C.S.** on Monday, October 15, 2012 at 11:20am.

y=x(sinx)(cosx)

- Calc -
**bobpursley**, Monday, October 15, 2012 at 11:22amy=uvw

y'=vwu' + uvw'+uwv'

It is just algebra, and probably some trig identities.

- Calc -
**Steve**, Monday, October 15, 2012 at 11:25amuse the product rule.

hard way:

(1)[(sinx)(cosx)] + {x(cosx)](cosx) + [x(sinx)](-sinx)

= sinx cosx + xcos^2 x - xsin^2 x

= 1/2 sin 2x + xcos 2x

easier way:

y = 1/2 x sin 2x

y' = 1/2 (sin 2x) + 1/2 x (2cos 2x)

= 1/2 sin 2x + x cos 2x

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