2₁)((cos(α-β)-((cosα)*(cosβ))/((cos(α+β)+(sinα)*(sinβ))=
((cosα*cosβ)+(sinα*sinβ)-(cosα*(cosβ))/((cosα)*(cosβ)-(sinα)*(sinβ)+(sinα)*(sinβ))=
(sinα/cosα)*(sinβ/cosβ)=(tgα)*(tgβ)
2₂) (tg(9π/16)-tg(5π/16))/(1+tg(9π/16)*(tg(5π/16))=tg((9π-5π)/16)=tgπ/4=1
