Упростите!
(ctg^2-cos^2)(1\cos^2 - 1)
(ctg^2-cos^2)(1\cos^2 - 1)=ctg^2/cos^2 - ctg^2 - cos^2/cos^2 + cos^2 = cos^2/sin^2 * 1/cos^2 - ctg^2 - 1 + cos^2 = 1+ctg^2 - ctg^2 - 1+cos^2 = cos^2
Формулы запомни:
sin^2+cos^2=1
1+ctg^2=1/sin^2
tg^2+1=1/cos^2