Q. 2
<span lang="EN-US
Answer :
False
cos2 23° - sin2 67° =(cos 23°+sin 67°)(cos 23°-sin 67°)
(∵(a2-b2) = (a+b)(a-b))
= [cos 23°+sin(90°-23°)] [cos 23°-sin(90°-23°)]
= (cos 23°+cos 23°)(cos 23°-cos 23°) (∵sin(90°-θ) = cos θ)
= (cos 23°+cos 23°).0
= 0, which is neither positive nor negative
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