1)cosa=-15/17,П/2<а<П Найти sina Tga Ctg

[latex]cosa=-15/17\ pi /2 extless a extless pi \tga=?\ctga=?\\ pi /a extless a extless pi = extgreater ain II(sina extgreater 0)\sina= sqrt{1-cos^2a}= sqrt{1-(-15/17)^2}= sqrt{1-(225/189)}= \=sqrt{64/289}=8/17\\tga=sina/cosa=8/17:(-15/17)=-8/15\ctga=1/tga=1/(-8/15)=-15/8 [/latex]