How do you verify $cos^2 2A = (1+cos4A)/2$ ?

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Answer 1 · 2016-05-11T17:57:50

see below

Use Property:
$cos2A=2cos^2A-1$

Right Hand Side : $=(1+cos4A)/2$

$=(1+cos2(2A))/2$

$=(1+(2cos^2(2A)-1))/2$

$=(1-1+2cos^2(2A))/2$

$=(cancel1-cancel1+2cos^2(2A))/2$

$=(2cos^2(2A))/2$

$=(cancel2cos^2(2A))/cancel2$

$=cos^2(2A)$

$=$ Left Hand Side

How do you verify cos^2 2A = (1+cos4A)/2cos^2 2A = (1+cos4A)/2?