1. (Tgx-1)(tgx+1)=0 2. 2sin^2x-3sinx-2=0 3. 2cos^2x+cosx-6=0

1) f(x) = ((sn (x))^2 + (cos (x))^2) = ((sn (x))^2) + ((cos (x))^2) = (sn (x)) * ((sn (x))^2) + (cos (x)) * ((cos (x))^2)= 2 * (cos (x)) * (sn (x)) 2 * (sn (x)) * (cos (x)) = 0.

2) f(x) = (1 + 16x^2 / аrсtg (4x)) = ((1 + 16x^2) * аrсtg (4x) + (1 + 16x^2) * (аrсtg (4x))) / (аrсtg (4x))^2 = (((1) + (16x^2)) * аrсtg (4x) + (1 + 16x^2) * (4x) * (аrсtg (4x))) / (аrсtg (4x))^2 = ((0 + 16 * 2 * x^1)) * аrсtg (4x) + (1 + 16x^2) * 4 * (1 / (1 + *(4х)^2))) / (аrсtg (4x))^2 = ((0 + 16 * 2 * x^1)) * аrсtg (4x) + (1 + 16x^2) * 4 * (1 / (1 + * (4х)^2))) / (аrсtg (4x))^2 = (32x * аrсtg (4x) + (1 + 16x^2) * (4 / (1 + * 16х^2))) / (аrсtg (4x))^2.

3) f(x) = (sn (x + sn (x)) = (x + sn (x)) * (sn (x + sn (x))) = ((x) + (sn (x))) * (sn (x + sn (x))) = (1 + cos (x)) * cos (x + sn (x)).