1) cos²a=1-sin²a=1-0,36=0,64 (4 четверть) cosa=0,8
ctga=cosa/sina=0,8/-0,6=-4/3 сtg²a=16/9
ctg2a=(ctg²a-1)/2ctga = (16/9-1)/-(8/3) = 7/9 *3/8 =21/72=-7/24
2) sin²a/2=(1-cosa)/2 = (1-7/18)/2 = 11/36 (2 четверть)
sina/2=√11/6
1) (3х²-2х)+( -х²+3х)=3х²-2х-х²+3х=2х²+х=х(2х+1)
2)(4с²-2cd)(-10c²+8cd)=4c²-2cd+10c²-8cd=14c²-10cd=2c(7c-5d
3)(12m²-7n-3mn)-(6mn-10n+14m²)= 12m²-7n-3mn-6mn+10n-14m²= 3n-2m²-9mn
4) (3n³-3mn+4m³)-(2mn+3n³)=3n³-3mn+4m³-2mn-3n³=4m³-5mn
17/24, 7/12, 3/4 вроде бы так