1) y'=(1/cos^2(x))(tgx)'=sec^2(x)y''=(sec^2(x))'=2sec(x)*sec(x)tgx=2sec^2(x)tgx
2) y'=(1/2sqrt(1+x^2))arctgx)'=(1/2sqrt(1+x^2))*(arctgx)'=(1/2sqrt(1+x^2))(1/(1+x^2))=1/2(1+x^2)^(-3/2)y''=(-3/2)(1+x^2)^(-5/2)(2x)=(-3x)(1+x^2)^(-5/2)
1) y'=(1/cos^2(x))(tgx)'=sec^2(x)
y''=(sec^2(x))'=2sec(x)*sec(x)tgx=2sec^2(x)tgx
2) y'=(1/2sqrt(1+x^2))arctgx)'=(1/2sqrt(1+x^2))*(arctgx)'=(1/2sqrt(1+x^2))(1/(1+x^2))=1/2(1+x^2)^(-3/2)
y''=(-3/2)(1+x^2)^(-5/2)(2x)=(-3x)(1+x^2)^(-5/2)