Срочно Вычислите а) tg^2a+ctg^2a,если tga - ctga = -4б) 1 +  2/tga+ctga,если cosa + sina =1/3

a) (tg a - ctg a)^2 = 16 = (tg a)^2 + 2*tg a * ctg a + (ctg a)^2 = [ tg a * ctg a = 1] = = (tg a)^2 + (ctg a)^2 +2 = 16 (tg a)^2 + (ctg a)^2 = 14 б) (cos a + sin a)^2 = 1/9 = (cos a)^2 + 2 sin a * cos a + (sin a)^2 = 1 + sin 2a sin 2a = -8/9 1 + 2/(tg a + ctg a) = 1+ 2/( sin a / cos a + cos a / sin a) = 1 + 2/ ( (sin^2 a + cos^2 a) / sin a*cos a) = 1+ 2 sin a*cos a/1 = 1+ sin 2a = 1 - 8/9 = 1/9