Chua Yong Qi's answer to girl's Secondary 4 A Maths Singapore question.
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use double angle formula twice
Date Posted:
3 years ago
thank you. how did you go from the second last to last step? like the 2cos^2 2x became cos4x -1+1 ?
the -1 is so that the expression will have 2cos^2(2x) - 1 (which is =cos4x by formula) . then the +1 is to "balance" out the -1, so that you do not change the expression.
(you can just change 2cos^2(2x) to cos4x +1 straight away, just different ways of presenting)
(you can just change 2cos^2(2x) to cos4x +1 straight away, just different ways of presenting)
I see, thank you :)
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