Sherming's answer to Justin Tan's Junior College 1 H1 Maths Singapore question.
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1e) MF26: 2cos^2 A -1 = cos2A
2cos^2 A = cos2A + 1
cos^2 A = 1/2 [ cos 2A+1]
sub into the qn,
1/2 [cos 2A + 1] = 1
cos 2A +1 = 2
cos 2A = 1
2A = cos-1 (1)
then just find A by dividing by 2 :)
(i used A instead of tita for simplification)
2cos^2 A = cos2A + 1
cos^2 A = 1/2 [ cos 2A+1]
sub into the qn,
1/2 [cos 2A + 1] = 1
cos 2A +1 = 2
cos 2A = 1
2A = cos-1 (1)
then just find A by dividing by 2 :)
(i used A instead of tita for simplification)
Date Posted:
3 years ago
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