How to prove 1 + Cos4x/2 = Cos22x .
How to prove 1 + Cos4x/2 = Cos22x .
Sam Abraham , 10 Years ago
Grade 12
Trigonometry> How to prove 1 + Cos4x/2 = Cos 2 2x ....
2 Answers
Kartik Sawant
1+cos4x/2= (1+2cos22x -1)/2 because cos2x=2cos2x -1
so =2cos22x/2 = cos22x. Hence the proof
so =2cos22x/2 = cos22x. Hence the proof
Akhil Chinnu
we know that cos2x=2cos2x -1
replace x by 2x
then cos4x=2cos22x -1
so,(1+2cos22x -1)/2
=(2cos22x)/2
=cos22x
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