sin^6x+cos^6x+3sin^2x*cos^2x+tg^2x

sin^6(x) + cos^6(x) + 3 * sin^2(x) * cos^2(x) = sin^6(x) + cos^6(x) + 3 * sin^2(x) * cos^2(x) * [ sin^2(x) + cos^2(x) ] = [sin^2(x) + cos^2(x) ]^3 = 1.