2. sin²γ+sinγ·cosγ·ctgγ=sin²γ+sinγ·cosγ·cosγ/sinγ=sin²γ+cos²γ=1;
3. (sinx-sin³x)/cos²x+2sinx=sinx(1-sin²x)/cos²x+2sinx=
=sinx·cos²x/cos²x +2sinx=sinx+2sinx=3sinx;
4. (5sinφ-3)/(4-5cosφ)-(4+5cosφ)/(3+5sinφ)=
=[(25sin²φ-9)-(16-25cos²φ)]/(4-5cosφ)(3+5sinφ)=
=(25sin²φ-25+25cos²φ)/(4-5cosφ)(3+5sinφ)=
=(25(sin²φ+cos²φ-1)/(4-5cosφ)(3+5sinφ)=0/(4-5cosφ)(3+5sinφ)=0