<span>{4х-3у=-1
{2x+4у=-6
{4x-3y=-1
</span>{4x+8у=-12
---------------------
11y=-11
y=-1
2x-4=-6
2x=-2
x=-1
ответ(-1;-1)
Cosx=-1/2
x=+-2Pi/3+2Pin, n∈Z
2у=4х-3
выбирай значения х от 0 до 3/4
х=0.5; у=-1
х=0.25; у=-2
х=0.1; у=-2.6
5. cos(П/5+2П/15)= cos П/3= 1/2
6.sin( 3П/8-5П/24)= sin 4П/24= sin П/6= 1/2
8. tg(13+32)= tg 45=1
9.tg(65-35)= tg 30=√3/3
10. tg (111+24)= tg 135= -1
11. tg( 67+83)= tg 150= √3/3
12. sin (7+47)/sin (13+41)= sin 54/sin54=sin1=П/2
13. cos (51+12)/ sin (13+14)= cos 63/sin27= сtg 7/3
14. (cos(105-75)-cos(105+75))/2= (cos30-cos180)/2= ((√3/2)+1)/2
15.(sin(П/24+7П/24)+sin(7П/24-П/24))/2= (sin 8П/24+sin(6П/24))/2= (sinП/3+sin П/4)/2= ((√3/2)+(√2/2))/2
16. (cos240 + cos30)/2= (-1/2+ 1/2)/2=0
17.2 cos 60*cos 45= 2* (√3/2) * (√2/2)