ctg(4110')=(22pi+150')=ctg(pi-30')=-ctg30'=-√3
0,5у-0,8у= -29+14
-0,3у= -15
у= -15:(-0,3)
у= 50.
Ответ: 50.
Решение:
tg66=tg(90-24)=ctg(24)
cos^2(114)=cos^2(90+24)=sin^2(24)
10cos^2114tg66=10sin^224*ctg24=5sin48
1-2cos^2111=-cos222=-cos(270-48)=+sin48
(1-2cos^2(111))/(10cos^2114*tg66)=sin48/5*sin48=1/5 или =0,2.
2c+5d-c+4d=c+9b
c=0.4 d=5.4= 5.8
2) a-b=0.12-1.28= 1.16
3) 2x+18y=-9+0.45
4) 8c-b=-2-21/2
X²-7x-18=0
D=49+72= 121
x1=(7+11)/2=9
x2=(7-11)/2= -2