1)1)sin330°= sin(270°+60°) = -cos60° = -1/2
2)cos240° = cos(180°+60°) = -cos60° = -1/2
В) S = ab
P = 2(a + b)
b = S/a = 28/a
P = 2(a + 28a) = 2a + 56/a = (2a^2 + 56)/a
a) P = 2(a + b) = 2a + 2b
b = (P - 2a)/2 = (16 - 2m)/2= 2(8 - m)/2 = 8 - m
S = ab = m(8 - m)
Вариант 2
№3
б) =(у-3х)(у+3х)/ -6х(у-3х)=- у+3х/6х
№4
х=-7+2у
3*(-7+2у)+5у=12
-21+6у+5у=12
11у=12+21
у=33/11
у=3
х=-7 +2*3= -7+6=-1
(2cos²x-1)(2cosx+1)+1=0
4cos³x+2cos²x-2cosx-1+1=0
2cosx(2cos²x+cosx-1)=0
cosx=0⇒x=π/2+πn
2cos²+cosx-1=0
cosx=a
2a²+a-1=0
D=1+8=9
a1=(-1-3)/4=-1⇒cosx=-1⇒x=π+2πn
a2=(-1+3)/4=1/2⇒cosx=1/2⇒x=+-π/3+2πn
x=π/2+πn;x=π+2πn;x=+-π/3+2πn