Eric Nicholas K's answer to Teck wee's Secondary 4 A Maths Singapore question.
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Date Posted:
4 years ago
Teck Wee, take note that for the 3rd step, the property used is :
cos2A = 2cos2²A - 1
then 1 + cos2A = 2cos²A
Followed by cos²A = (1 + cos2A)/2
So for cos²2A, it equals = (1 + cos2(2A))/2
= (1 + cos4A)/2
cos2A = 2cos2²A - 1
then 1 + cos2A = 2cos²A
Followed by cos²A = (1 + cos2A)/2
So for cos²2A, it equals = (1 + cos2(2A))/2
= (1 + cos4A)/2
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