⇒x²-x+6=0 или x²+x-6=0
1) <span>x²-x+6=0
D=1-4*6=-23<0 </span>⇒ не имеет решения
2) <span>x²+x-6=0
D=1+6*4=25
x1=(-1+5)/2=2
x2=(-1-5)/2=-3
ответ: 2 и -3</span>
Cosx = 1 - sin^2x
sinx = -2√(2/3)
3cosx = 3 - 3*(-2√(2/3) = 3 - 6√(2/3)
2) sinx = 270
cosx = 1 - (sin^2)[270] = 1 - (√3/2)^2 = 1 - 3/2 = - 1/2
2). y= -5*(-0,8)+1,2=4+1,2=5,2. 3). 0,2x-3,6= -2,4; 0,2x=1,2; x=1,2/0,2=6.
Sin 54- sin 18 = 2 sin (54-18 /2) *cos (54+18)/2=2 *sin18*cos72=2 sin^2(18)=1-cos36=
=1-(1+√5)/4
=(3-√5)/4
=3/4-√5/4