`cos8 0^0+cos4 0^0-cos2 0^0=0`

Prove that: cos 80^0+cos 40^0-cos 20^0=0

Prove that: cos 80^0+cos 40^0-cos 20^0=0

Prove that: cos 80^0+cos 40^0-cos 20^0=0

Prove that: cos 20^0+cos 100^0+cos 140^0=0

Prove that: \ cos 20^0cos 40^0cos 80^0=1/8

Prove that: cos 20^0cos 100^0+cos 100^0cos 140^0-\ cos 140^0cos 200^0=-3/4

Prove that : cos 20^0cos 40^0cos 60^0cos 80^0=1/(16)

cos20^0+cos80^0-sqrt(3)cos50^0 p. -1 cos0^0+cospi/7+cos(2pi)/7+cos(3pi)/7+cos(4pi)/7+cos(5pi)/7+cos(6pi)/7 q. -3/4 cos20^0+cos40^0+cos60^0-4cos10^0cos20^0cos30^0 r. 1 cos20^0cos100^0+cos100^0cos140^0-cos140^0cos200^0 s. 0

Prove that: cos 100^0+cos 20^0=cos 40^0

Prove that: cos 10^0cos30^0cos 50^0cos 70^0=3/(16)