`cos pi/5+cos(2pi)/5+cos(6pi)/5+cos(7pi)/5`=0

cospi/5+cos(2pi)/5+cos(6pi)/5+cos(7pi)/5=0

Prove that: cos(pi/5)cos((2pi)/5)cos((4pi)/5)cos((8pi)/5)=(-1)/16

Prove: cos(pi/15)cos((2pi)/15)cos((3pi)/15)cos((4pi)/15)cos((5pi)/15)cos((6pi)/15)cos((7pi)/15) = 1/2^7

Show that cos(pi/15)cos((2pi)/15)cos((3pi)/15)cos((4pi)/15)cos((5pi)/15)cos((6pi)/15)cos((7pi)/15) = 1/2^7

"cos(pi/15)cos((2pi)/15)cos((4pi)/15)cos((8pi)/15)=k

cos(pi/65)cos((2pi)/65)cos((4pi)/65)cos((8pi)/65)cos((16pi)/65)cos((32pi)/64)=1/64

Show that cos(pi/65)cos((2pi)/65)cos((4pi)/65)cos((8pi)/65)cos((16pi)/65)cos((32pi)/65)=1/64

Find the value of cospi/7+cos(2pi)/7+cos(3pi)/7+cos(4pi)/7+cos(5pi)/7+cos(6pi)/+cos(7pi)/7

The value of cos(pi/7)+cos((2pi)/7)+cos((3pi)/7)+cos((4pi)/7)+cos((5pi)/7)+cos((6pi)/7)+cos((7pi)/7) is 1 (b) -1 (c) 0 (d) none of these

Statement-1 : "cos"pi/7+"cos"(2pi)/7+"cos"(3pi)/7+"cos"(4pi)/7+"cos"(5pi)/7+"cos"(6pi)/7 vanishes Statement-2 : Sum of the cosines of two supplementary angles vanishes.