Question

1+ tga1+ctga , если cosa=1215 , 3п2 < a < 2п

Answer 1

$sin alpha =- sqrt{1- frac{144}{225} }=- frac{9}{15}$
$tg alpha = frac{sin alpha }{cos alpha } =- frac{9*15}{15*12} = - frac{9}{12} =- frac{3}{4}$
$ctg alpha = frac{1}{tg alpha }=- frac{4}{3}$
$1+ frac{- frac{3}{4} }{1- frac{4}{3}} =1+ frac{3*3}{4*1}=1+2.25=3.25$