sina=√(1-cos²a)=√(1-144/169)=√(25/169)=5 /13
tga=sina/cosa-5/13:12/13-5/13*13/12=5/12 tg(π/4+a)=(tga+tgñ/4)/(1-tga*tgn/ 4)=(5/12+1):(1-5/12*1)=17/12:7/12=17/12*12/7=
=17/7
