Question

cot⁴theita -sin⁴theita is equal to
explain
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Answer 1

Answer:

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Step-by-step explanation:

1) 1 + 2 sin2(θ/2)

2) 2 cos2θ – 1

3) 1 – 2 sin2(θ/2)

4) 1 + 2 cos2θ

Answer: (2) 2 cos2θ – 1

Solution:

cos4θ – sin4θ

= (cos2θ)2 – (sin2θ)2

= (cos2θ + sin2θ)(cos2θ – sin2θ)

= 1(cos2θ – sin2θ)

= cos2θ – (1 – cos2θ)

= 2 cos2θ – 1