Question
Which of the following options are equal to cos2A−sin2A ?
Answer: Option A
:
A and D
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:
A and D
We know that, sin2A+cos2A=1.
1) cos2A−sin2A=(1−sin2A)−sin2A
=1−2 sin2A
2) cos2A−sin2A=cos2A−(1−cos2A)
=cos2A−1+cos2A
=2 cos2A−1
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