ctg(pi/12)=koren((1+cos(pi/6))/(1-cos(pi/6)))= =koren((2+koren(3))/(2-koren(3)))=(2+koren(3))/koren(4-3)=2+koren(3).
примерно 0,9659tg 15=sin15/cos15
ctg(pi/12)=koren((1+cos(pi/6))/(1-cos(pi/6)))=
sin(75) = cos(90 - 75) = cos(15)=koren((2+koren(3))/(2-koren(3)))=(2+koren(3))/koren(4-3)=2+koren(3).
примерно 0,9659
tg 15=sin15/cos15