Question #0373f

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Answer 1 · 2017-03-11T07:12:32

$sin 2x sin x - cos 2x cos x =-cos x$

$=>cos 2x cos x-sin 2x sin x =cos x$

$=>cos (2x + x) =cos x$

$=>cos (3x) =cos x$

$=>3x=2npipmx" where "n in ZZ$

So

when

$=>3x=2npi+x" where "n in ZZ$

$=>2x=2npi" where "n in ZZ$

$=>x=npi" where "n in ZZ$

Again when

$=>3x=2npi-x" where "n in ZZ$

$=>4x=2npi" where "n in ZZ$

$=>x=(npi)/2" where "n in ZZ$