Question

help friends please please please please please help me..........give ans with solution.....................
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Answer 1

the answer of the question is d)none of the above

because cos90=0 and there is neither cos90 nor 0 in the three options so d)

Answer 2

$\cos(1) \cos(2) \cos(3) ......... \cos(90) ..... \cos(180) \\ \cos(90) = 0 \\ whole \: term \: will be \: zero$

options d is right