" 9.Show that "(1+cos(pi)/(9))(1+cos(3 pi)/(9))(1+cos(5 pi)/(9))(1+cos(7 pi)/(9))=(9)/(16)

The value of (1+cos((pi)/(9)))(1+cos((3 pi)/(9)))(1+cos((5 pi)/(9)))(1+cos((7 pi)/(9)))

Show that (1+"cos"pi/9).(1+"cos"(3pi)/9).(1+"cos"(5pi)/9).(1+"cos"(7pi)/9)=9/16

Hence deduce that cos(pi)/(9)cos(2 pi)/(9)cos(3 pi)/(9)cos(4 pi)/(9)=(1)/(16)

Prove that (1+cos pi/9) (1 + cos 3pi/9) (1+ cos 5pi/9) (1 + cos 7pi/9) =9/16 .

cos (pi)/(11)+cos (3 pi)/(11)+cos (5 pi)/(11)+cos (7 pi)/(11)+cos (9 pi)/(11)=

Prove that: (1+ cos ""(pi)/(10)) (1+ cos ""(3pi)/(10)) (1+ cos ""(7 pi)/(10)) (1+ cos""(9 pi)/(10))=(1)/(16)

Prove that: 8(cos^(3)pi)/(9)-6(cos pi)/(9)=1

Prove that (1+cos(pi/10))(1+cos(3pi/10))(1+cos(7pi/10))(1+cos(9pi/10))=1/16

Prove that cos ""(pi)/(9) cos ""( 2pi)/(9) cos "" (3pi)/(9) cos ""(4pi)/(9) = (1)/(2 ^(4)).