Question

cos36°cos72°-cos108°cos144°​

Answer 1

Answer:Value of cos36 = [(√3+1)/2√2]

Value of sin18 = [(√3-1)/2√2]

Now,

=cos36×cos72×cos108×cos144

=cos36×sin(90-18)×cos(90+18)×cos(180-36)

=cos36×sin18×(-sin18)×(-cos36)

=cos36sin18sin18cos36

=[(√3+1)/2√2][(√3-1)/2√2}[(√3-1)/2√2][(√3+1)/2√2]

=2/8×2/8

=1/16

Step-by-step explanation:

Answer 2

Answer ⤵️

cos36° sin (90°-36°) - cos(144° -108°)

cos36° .cos36. - cos 36°

=1-cos36°

hence your answer will be = 1- cos36°..

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