Question

$1 + \cos(2 \alpha ) + \cos(4 \alpha ) + \cos(6 \alpha )$
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Answer 1

The answer is in Attachment

thank you

Answer 2

Answer: 4 cos a cos 2a cos 3a

Step-by-step explanation:= 1 + cos 2a + cos 4a + cos 6a  

= ( 1 + cos 4a ) + ( cos 6a + cos 2a )  

= [ 2 cos² ( 4a/2 ) ] + 2 cos [ ((6a)+(2a))/2 ] · cos [ ((6a)-(2a)) / 2 ]  

= 2 cos² 2a + 2 cos 4a cos 2a  

= 2 cos 2a [ cos 4a + cos 2a ]  

= 2 cos 2a [ 2 cos 3a cos a ]  

= 4 cos a cos 2a cos 3a