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The value of

cos(2pie/7) + cos(4pie/7) + cos(6pie/7) + cos(7pie/7)

1. 1
2. -1
3. 0.5
4. -1.5

cmon guys kill it....its an easy 1 i think

10 Answers

1
Akshay Pamnani ·

4
-1.5

1
Manas ·

yah correct i think

1
prateek punj ·

i think it's (4).....aaj test main aaya tha.....

13
deepanshu001 agarwal ·

yes....

i hav the ans....gimme the soln....

1
°ღ•๓яυΠ·

it has a shrt cut :P

13
deepanshu001 agarwal ·

then wud u plz lyk 2 tel it 2 me..

1
kamalendu ghosh ·

1357
Manish Shankar ·

cos(2pie/7) + cos(4pie/7) + cos(6pie/7)+cos(8pie/7) + cos(10pie/7) + cos(12pie/7)=-1 (sum of roots of x7=1)

2(cos(2pie/7) + cos(4pie/7) + cos(6pie/7))=-1

cos(2pie/7) + cos(4pie/7) + cos(6pie/7)=-1/2

cos(2pie/7) + cos(4pie/7) + cos(6pie/7)+cos(7pie/7)=-1/2-1=-1.5

13
deepanshu001 agarwal ·

tht ws smart.....!!!

1
kamalendu ghosh ·

in post #8 ...sorry i messed it up!! the formula is the same but interchange sin and cos

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