1)=cos^2 a*(sin^2a/cos^2 a)=sin ^2 a 2)cosa=coren(1-(-12/13)^2)=coren25/13=5/13; (4-aя четверть)
3)=-(cos^2 a-sin^2a)-1=-cos2a-1
|cos2a|+<1, -1=<-cos2a=,1 -2=<cos2a<=2 Ответ. -2 4)<br> 4)=sinacosb-sinacosb+sinbcosa=sinbcosa; 1)
5)=coren2cos(2*pi/8)=coren2 *cospi/4= coren2 *(coren2/2)=2/2=1
6)(sin(pi+pi/4)-cs(pi-pi/4) tg(2pi+pi/3)=(-sinpi/4-cospi//)*tgpi/3=-coren2*coren3=-coren6