28a+13b-13=5(5a+6b-6)
28a+13b-13=25a+30b-30
3a-17b=-17
3a-17b+28=-17+28=11
Sin2x + V2 sinx = 0
2sin x cos x + V2 sinx = 0
sinx (2 cos x + V2) = 0
a)sinx = 0 , 2cos x= -V2
x = pin, n E z
2cos x = -V2
cos x = -V2/2
x = +-3pi/4 + 2pin, n E z
n = 1
x1 = pi
x2 = +-3pi/4 + 2pi = 2pi - 3pi/4 = 5pi/4
n=0
x3 = +-3pi/4
Ответ pi, 5pi/4, +-3pi/4
<u>б</u>) V3cos^2 x - 0,5 cos(3pi/2 + 2x) = V3cos^2 x - 0.5 sin2x = V3cos^2x - sin x cos x = cos x (V3 cos x - sinx)
в) cos2x = Tg^2 x - cos^2 x
cos^2 x - sin^2 x = tg^2 x - cos^2 x
2cos^2 x - sin^2 x = tg^2 x
cos x <= 1/2
x <= +- pi/6 + 2pin
1%-0,4км
100%-20%-45%=35%(по лесной дороге)
35*0,4=14(км)
12/8 = 1 4/8
20/16=1 4/16
35/25= 1 10/25
46/32 = 1 14/32
56/12 = 4 8/12
105/45 = 2 15/45
90/65= 1 25/65