" 4.Prove that "(666cdots6)^(2)+(888cdots8)=4444cdots4

Prove that (666...6)^(2)+(888dots8)=4444...4

Prove that (666....6)^2+(888....8)=4444.....4.

Prove that (666....6)^2+(888....8)=4444.....4.

Prove that (666 ....6)^2+(888 .....8)=4444 ...... 4.

Prove that "cos" (2pi)/15 cdot "cos"(4pi)/15 cdot "cos" (8pi)/15 "cos"(14pi)/15=1/(16)

Prove that : (2^(1/4)cdot4^(1/8)cdot8^(1/16)cdot16^(1/32)......oo)=2

Prove that, tan^(2) (pi/6) cdot tan^(2)(2pi/16) cdot tan^(2) (3pi/16) cdot tan^(2) (4pi/16) cdot tan^(2) (5pi/16) cdot tan^(2) (6pi/16) cdot tan^(2)(7pi/16) = 1 .