Think of a celebration you enjoyed a lot. Describe it to the class. Talk about: what the celebration was, where/when it happened, who was there, how you felt.

По формуле tg(A+B)= (tgA+tgB)/(1-tgA *tgB)=(3-2)/(1-3*(-2))=1/7

ctg(A-B)=1/tg(A-B)=1 / ((tgA-tgB)/(1+tgA*tgB)) =(1+tg A tg B)/(tgA-tgB)=(1+3*(-2))/(3-(-2))= -5/5= - 1