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4. The value of 16 cos(2π/15) cos(4π/15) cos(8π/15) cos(16π/15) is (a) 1 (b) 3 (c) -1 (d) None of these please explain

4.     The value of 16 cos(2π/15)  cos(4π/15) cos(8π/15) cos(16π/15) is


(a)    1


(b)    3


(c)    -1


(d)    None of these


please explain

Grade:11

1 Answers

Souradeep Majumder
80 Points
13 years ago

i thnk the answer is -1...... 

 

get a tricks

the no of cos function is 4.........  ans 1/2^4....................  if we multiply 8*2 then its values is 16 which exceeds 15...........  so sign is negative....................  if you like my answer please please approve it...........  its a very good tricks..........

 

the mod of the value is 1.........  but i dont emember its -1 or +1.........  if it is -1 then its the tricks.............  if it is +! then sign system is applicable for  only sin function............

 

thanks............  approve it..............

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