Question

sin^4a+2sin^2a*cos^2a+cos^4a

Answer 1

$sin^4a+2sin^2a*cos^2a+cos^4a= (sin^2a+cos^2a)^2=1^2=1$

Answer 2

$sin ^{4} a+2sin ^{2} a*cos ^{2} a+cos ^{4} a= (sin ^{2} a+cos ^{2} a) ^{2} = \\ =1 ^{2} =1$