LHS is nothing but (using sin (a+b) = sin a cos b + cos a sin b)
sin (x+2x) = sin 3x = 0
so 3x = npi
or
x = npi/3
The answer is x = n p i divided by 3
To solve sin x cos 2 x + cos x sin 2 x = 0 , we rewrite it as sin ( 3 x ) = 0 . The solutions are given by x = 3 nπ , or in degrees, x = 0° , 60° , 120° , 180° , 240° , 300° , … .
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