alleryStart learning →Which of these is NOT a valid form of cos 2θ?
Acos²θ − sin²θ
B2 cos²θ − 1
C1 − 2 sin²θ
D2 sin²θ − 1
Answer & Solution
Correct answer: D. 2 sin²θ − 1
cos2θ equals cos²θ − sin²θ, 2cos²θ − 1 and 1 − 2sin²θ, whereas 2sin²θ − 1 is the negative of the last form.
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