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March 27, 2015

March 27, 2015

Posted by **greg** on Monday, December 3, 2012 at 10:19am.

Hint: the following substitution should come in handy: sin3x= cos3x . tan3x

- math -
**Steve**, Monday, December 3, 2012 at 11:00amsin2x + sin4x = 2sin3x cosx

cos2x + cos4x = 2cos3x cosx

so, we have

sin3x cosx = cos3x cosx

tan3x = 1

so, 3x = pi/4 or 5pi/4

x = pi(1+4k)/12 for all 0<=k<=5

also x=k*pi/2 (where cosx = 0)

- math -
**teti**, Wednesday, March 18, 2015 at 7:00amcos4x-cos2x=sin4x-sin2x

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